Re: Some OSPF Questions
If you look at page 432, Table 9.1 in Doyle's "Routing TCP/IP" for the OSPF interface state machine, you will see clearly that one of the events (6). is "the expiration of the RouterDeadInterval without having received a Hello from the DR or the BDR or both", which changes directly to the DR/BDR election state. This implies that the DR/BDR election process is associated with the Hello interval, not an LSA. It makes sense, because every Hello packet states the DR and the BDR. If the DR goes down, how does it send an LSA to notify anybody about it? I am not sure exactly what a "missed LSA" means in this regard. The state diagram is probably the source from which that actual software algorithms were derived. JMHO MLC "David Armstrong" <[EMAIL PROTECTED]> wrote in message 8up5n1$src$[EMAIL PROTECTED]">news:8up5n1$src$[EMAIL PROTECTED]... > This has been an awesome thread to me. Thanks everyone for the input. > Evidently I'm not alone in being confused over BDR to DR promotion. The > books and literature I've found have clearly stated that the event to > promote BDR's to DR's is a missed LSA; however, the tests here show > otherwise. Winston, I'm with you: I hope they never ask this on the test. > I'll have to decide between what I believe to be right and what the book > states as right. > > I still think there's a piece missing. 40 seconds to take over the functions > of DR seems like it could create routing delays or time outs on a large > network. I'm going to continue to look for a definitive answer. > > Thanks Again, > > David > > ""David Armstrong"" <[EMAIL PROTECTED]> wrote in message > 8uh8vj$c47$[EMAIL PROTECTED]">news:8uh8vj$c47$[EMAIL PROTECTED]... > > Last night at our BSCN study group meeting in Dallas we had some questions > > about OSPF that we weren't able to resolve. If someone or ones could > answer > > these it would clarify some areas we're a little fuzzy on. Also, if you're > > iin the Dallas Ft. Worth area and would like to attend, we'd love to have > > you join us.. > > > > Thanks for any help, > > > > David Armstrong > > > > > > 1) What is the default time period that the BDR waits when listening to > > LSA's from the DR before it decides that the DR is down and promotes > itself > > to DR. All the literature we could find simply said that the BDR waits for > > the specified time period but never said what that period is. > > > > 2) In a Point-to-Point network in which the router in Area 0 is connected > to > > FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and > > updates take place? From what we've found a DR and BDR is not elected in a > > strictly Point-to-Point network. > > > > I think an example would explain this question better: We have one 3620 > > router in our Ft. Worth office connected to an office in Houston (via FR), > > and office in Kansas City (via FR), an office in the DFW area (via ISDN) > and > > the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and > the > > firewall is connected to a 1720 going to the Internet. I'd like to > implement > > OSPF on our network simply for the experience. However, I don't have 2 > > routers internally on our Ethernet LAN that can be configured for Area 0 > and > > elected to DR and BDR. All other routers connected to that router are via > > NBMA Point-to-Point connections. Since I only have one router on the > > Broadcast Multiaccess network (the 3620) and routers connected via PtoP > > don't participate in DR and BDR elections, how would updates occur? Can > > their only be one DR (in this case the 3620)? > > > > 3) The books and tutorials all state that "router ospf 6" defines ospf on > > the router with a process ID of 6. They then all say that you shouldn't > > define more than one process. Does that mean that you can have a router > with > > the following: > > > > router ospf 6 > > network 10.100.0.0 0.0.255.255 > > > > router ospf 7 > > network 10.200.0.0 0.0.255.255 > > > > If this is an allowed configuration, what kind of instances would it be > used > > for? Also, exactly what is the process ID used for? > > > > > > > > > > _ > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Some OSPF Questions
"David Armstrong" <[EMAIL PROTECTED]> wrote, >This has been an awesome thread to me. Thanks everyone for the input. >Evidently I'm not alone in being confused over BDR to DR promotion. The >books and literature I've found have clearly stated that the event to >promote BDR's to DR's is a missed LSA; however, the tests here show >otherwise. Winston, I'm with you: I hope they never ask this on the test. >I'll have to decide between what I believe to be right and what the book >states as right. I'd be surprised if it were asked. In general, however, take the RFC over any review materials. In this case, though, I will quote a bit from John Moy's _OSPF: Anatomy of an Internet Routing Protocol_ book. John is the principal author/editor of the OSPF specification. There really is more than one failure mode to consider: (Moy p 106) "If the DR fails, so does database synchronization over the broadcast subnet. OSPF deals with this problem by electing a BDR for the broadcast subnet. All routers synchronize with both the DR and BDR, and the BDR acts as a hot standby in case the DR fails." (Moy p 107) " ...if the BDR does not see the Link State Update from the DR within the LSA retransmission interval (typically 5 seconds), it will step in and flood the LSA back onto the Ethernet in order to keep the database synchronization going. " So, if active updating is going on, the BDR will act to keep that process working before a DR is elected. The absence of a DR, especially when the subnet is otherwise idle, will be detected by missing hellos, by the dead timer. >I still think there's a piece missing. 40 seconds to take over the functions >of DR seems like it could create routing delays or time outs on a large >network. I'm going to continue to look for a definitive answer. You are pointing to a very real problem in available protocols. See http://www.nanog.org/mtg-0010/ppt/cengiz.pdf for some research approaches to subsecond convergence times. > >Thanks Again, > >David > >""David Armstrong"" <[EMAIL PROTECTED]> wrote in message >8uh8vj$c47$[EMAIL PROTECTED]">news:8uh8vj$c47$[EMAIL PROTECTED]... >> Last night at our BSCN study group meeting in Dallas we had some questions >> about OSPF that we weren't able to resolve. If someone or ones could >answer >> these it would clarify some areas we're a little fuzzy on. Also, if you're >> iin the Dallas Ft. Worth area and would like to attend, we'd love to have >> you join us.. >> >> Thanks for any help, >> >> David Armstrong >> >> >> 1) What is the default time period that the BDR waits when listening to >> LSA's from the DR before it decides that the DR is down and promotes >itself >> to DR. All the literature we could find simply said that the BDR waits for >> the specified time period but never said what that period is. >> >> 2) In a Point-to-Point network in which the router in Area 0 is connected >to >> FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and >> updates take place? From what we've found a DR and BDR is not elected in a >> strictly Point-to-Point network. >> >> I think an example would explain this question better: We have one 3620 >> router in our Ft. Worth office connected to an office in Houston (via FR), >> and office in Kansas City (via FR), an office in the DFW area (via ISDN) >and >> the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and >the >> firewall is connected to a 1720 going to the Internet. I'd like to >implement >> OSPF on our network simply for the experience. However, I don't have 2 >> routers internally on our Ethernet LAN that can be configured for Area 0 >and >> elected to DR and BDR. All other routers connected to that router are via >> NBMA Point-to-Point connections. Since I only have one router on the >> Broadcast Multiaccess network (the 3620) and routers connected via PtoP >> don't participate in DR and BDR elections, how would updates occur? Can >> their only be one DR (in this case the 3620)? >> >> 3) The books and tutorials all state that "router ospf 6" defines ospf on > > the router with a process ID of 6. They then all say that you shouldn't >> define more than one process. Does that mean that you can have a router >with >> the following: >> >> router ospf 6 >>network 10.100.0.0 0.0.255.255 >> >> router ospf 7 >> network 10.200.0.0 0.0.255.255 >> >> If this is an allowed configuration, what kind of instances would it be >used >> for? Also, exactly what is the process ID used for? >> >> >> >> >> _ >> FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] >> > > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list
Re: Some OSPF Questions
This has been an awesome thread to me. Thanks everyone for the input. Evidently I'm not alone in being confused over BDR to DR promotion. The books and literature I've found have clearly stated that the event to promote BDR's to DR's is a missed LSA; however, the tests here show otherwise. Winston, I'm with you: I hope they never ask this on the test. I'll have to decide between what I believe to be right and what the book states as right. I still think there's a piece missing. 40 seconds to take over the functions of DR seems like it could create routing delays or time outs on a large network. I'm going to continue to look for a definitive answer. Thanks Again, David ""David Armstrong"" <[EMAIL PROTECTED]> wrote in message 8uh8vj$c47$[EMAIL PROTECTED]">news:8uh8vj$c47$[EMAIL PROTECTED]... > Last night at our BSCN study group meeting in Dallas we had some questions > about OSPF that we weren't able to resolve. If someone or ones could answer > these it would clarify some areas we're a little fuzzy on. Also, if you're > iin the Dallas Ft. Worth area and would like to attend, we'd love to have > you join us.. > > Thanks for any help, > > David Armstrong > > > 1) What is the default time period that the BDR waits when listening to > LSA's from the DR before it decides that the DR is down and promotes itself > to DR. All the literature we could find simply said that the BDR waits for > the specified time period but never said what that period is. > > 2) In a Point-to-Point network in which the router in Area 0 is connected to > FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and > updates take place? From what we've found a DR and BDR is not elected in a > strictly Point-to-Point network. > > I think an example would explain this question better: We have one 3620 > router in our Ft. Worth office connected to an office in Houston (via FR), > and office in Kansas City (via FR), an office in the DFW area (via ISDN) and > the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and the > firewall is connected to a 1720 going to the Internet. I'd like to implement > OSPF on our network simply for the experience. However, I don't have 2 > routers internally on our Ethernet LAN that can be configured for Area 0 and > elected to DR and BDR. All other routers connected to that router are via > NBMA Point-to-Point connections. Since I only have one router on the > Broadcast Multiaccess network (the 3620) and routers connected via PtoP > don't participate in DR and BDR elections, how would updates occur? Can > their only be one DR (in this case the 3620)? > > 3) The books and tutorials all state that "router ospf 6" defines ospf on > the router with a process ID of 6. They then all say that you shouldn't > define more than one process. Does that mean that you can have a router with > the following: > > router ospf 6 > network 10.100.0.0 0.0.255.255 > > router ospf 7 > network 10.200.0.0 0.0.255.255 > > If this is an allowed configuration, what kind of instances would it be used > for? Also, exactly what is the process ID used for? > > > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Some OSPF Questions
OK, first a big thanks to everyone who contributed to this one as well as those watching from the sidelines. I believe we're very close to having this one figured out and here's how I've come to this conclusion: I recreated Chuck's experiment with 3 routers on an ethernet segment. I also simultaneously ran a sniffer on the segment to determine what's going on for the 40 seconds or so while the DR is unavailable--that does seem like an awfully long time. So I ran "debug ip ospf events" on the BDR and ovserved the output. Things looked normal--regular send/receipt of Hellos--then I removed the cable connecting the DR from the hub and observed the output. Just what you'd expect...in 40 seconds an election took place..BDR became the DR and the only DROther was now the BDR. Well one odd thing ...the box made a note to "remember" the old DR as indicated by this event msg: 03:16:25: OSPF: Remember old DR 192.2.2.1 (id) I found this odd and I really have no explaination for it?? But the key point is that review of the sniffer capture showed that 5 packets after the DR stopped sending hellos the BDR began sending acks to the DROther on LSAs--as best I can tell, at this time it was still the BDR. CONCLUSION: The process of DR/BDR election after a DR is declared dead appears to be completely independent of the BDR "backing-up" the DR in performance of it's duties. It seems even though the BDR has assumed the "duties" of the DR it remains the BDR until the dead timer expires. While I still don't know the timeframe precisely I must admit the 0.5 second answer given earlier seems like a reasonable SWAG. Any comments are appreciated...Frank "Shaw, Winston Mr." wrote: > > Chuck, > Thanks for testing. Now my curiosity is at an all time high. Is it possible > for you to do the test with 4 routers ? > My theory is that 2 or maybe even 3 routers are not enough. > Here is why: 2 routers on a broadcast net will always have a DR and BDR. If > the DR goes away, the DR will know it is alone on a broadcast net. It will > become a DR in its own right. It will not be taking over any duties of the > former DR. The time to realize that it is alone will be 40 secs(default). A > 3 router net might have the same issue. The absence of the DR will trigger a > promotion of the BDR. The remaining router will become the BDR. This seems > to be consistent with the broadcast net rules. > > Although the code obviously selects BDRs and DRs very early, maybe the > duties of DR flooding do not start until there is at least one other DRother > on the net. > > I only have two routers available and my test produced essentially the same > results as yours. Something I did notice is that the Network type 2 LSAs > never aged. > If a 4 router test produces the same results then it will be difficult to > say whether LSAs or hello packets determine when the BDR takes over for the > dead DR. I hope they never ask this question on any test. > > Winston. > > -Original Message- > From: Chuck Larrieu [mailto:[EMAIL PROTECTED]] > Sent: Saturday, November 11, 2000 8:39 PM > To: Matthew Herman; David Armstrong; [EMAIL PROTECTED] > Subject: RE: Some OSPF Questions > > Just to put in some empirical data, I set up two routers on an Ethernet > link, in the classic OSPF broadcast scenario. Hello time is 10 seconds. Dead > time 40 seconds ( 4xhello ) > > I determined which of the two routers was the DR, and which was the BDR > > I then plugged into and monitored from the BDR, using repeated "show ip ospf > neighbor" commands > > I then unplugged the DR from the ethernet > > I then repeatedly reissued the show ip ospf neighbor commands > > I watched. > > The result of the show command was that the neighbor state FULL/DR remained > in effect until the dead time was reached. After that, there was no > neighbor. > > I also plugged it the first router back into the ethernet and repeatedly > issued the commands. After a few seconds the first router showed up as a > FULL/BDR > > Of some interest - the debug ip ospf hello and debug ip ospf events were > silent immediately after unplugging the DR. It was only after the expiration > of the dead time that debug ip ospf events indicated the election of a new > DR, to whit, the router I was monitoring. > > Where this 0.5 second / half second thing comes from I cannot say. But using > Cisco's defaults in a quick and dirty lab, it is safe to say that this is > not what happens. > > Chuck > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of > Matthew Herman > Sent: Friday, November 10, 2000 9:56 AM > To: David Armstrong; [EM
Re: Some OSPF Questions
If you look at the RFC, I believe there are only BDR elections. When a new segment comes up, a BDR is elected, then promoted to DR, then the BDR is elected again. Ed > Of some interest - the debug ip ospf hello and debug ip ospf events were > silent immediately after unplugging the DR. It was only after the expiration > of the dead time that debug ip ospf events indicated the election of a new > DR, to whit, the router I was monitoring. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Some OSPF Questions
Chuck, Thanks for testing. Now my curiosity is at an all time high. Is it possible for you to do the test with 4 routers ? My theory is that 2 or maybe even 3 routers are not enough. Here is why: 2 routers on a broadcast net will always have a DR and BDR. If the DR goes away, the DR will know it is alone on a broadcast net. It will become a DR in its own right. It will not be taking over any duties of the former DR. The time to realize that it is alone will be 40 secs(default). A 3 router net might have the same issue. The absence of the DR will trigger a promotion of the BDR. The remaining router will become the BDR. This seems to be consistent with the broadcast net rules. Although the code obviously selects BDRs and DRs very early, maybe the duties of DR flooding do not start until there is at least one other DRother on the net. I only have two routers available and my test produced essentially the same results as yours. Something I did notice is that the Network type 2 LSAs never aged. If a 4 router test produces the same results then it will be difficult to say whether LSAs or hello packets determine when the BDR takes over for the dead DR. I hope they never ask this question on any test. Winston. -Original Message- From: Chuck Larrieu [mailto:[EMAIL PROTECTED]] Sent: Saturday, November 11, 2000 8:39 PM To: Matthew Herman; David Armstrong; [EMAIL PROTECTED] Subject: RE: Some OSPF Questions Just to put in some empirical data, I set up two routers on an Ethernet link, in the classic OSPF broadcast scenario. Hello time is 10 seconds. Dead time 40 seconds ( 4xhello ) I determined which of the two routers was the DR, and which was the BDR I then plugged into and monitored from the BDR, using repeated "show ip ospf neighbor" commands I then unplugged the DR from the ethernet I then repeatedly reissued the show ip ospf neighbor commands I watched. The result of the show command was that the neighbor state FULL/DR remained in effect until the dead time was reached. After that, there was no neighbor. I also plugged it the first router back into the ethernet and repeatedly issued the commands. After a few seconds the first router showed up as a FULL/BDR Of some interest - the debug ip ospf hello and debug ip ospf events were silent immediately after unplugging the DR. It was only after the expiration of the dead time that debug ip ospf events indicated the election of a new DR, to whit, the router I was monitoring. Where this 0.5 second / half second thing comes from I cannot say. But using Cisco's defaults in a quick and dirty lab, it is safe to say that this is not what happens. Chuck -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Matthew Herman Sent: Friday, November 10, 2000 9:56 AM To: David Armstrong; [EMAIL PROTECTED] Subject: RE: Some OSPF Questions I'll throw my hat in.. 1. .5 seconds (50 msec) (Chapter 7, p142 exam cram acrc) 2. yes, there will be only one DR and its your single point of failure as well 8->. 3. doh...I have set up multiple as's on one router when I had multiple customer and redistributed into my AS. It worked ok but I am not saying that was a good way of configuring the router. 2/3 = 66 percent Still not enough to pass the ccie... matt -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of David Armstrong Sent: Friday, November 10, 2000 8:46 AM To: [EMAIL PROTECTED] Subject: Some OSPF Questions Last night at our BSCN study group meeting in Dallas we had some questions about OSPF that we weren't able to resolve. If someone or ones could answer these it would clarify some areas we're a little fuzzy on. Also, if you're iin the Dallas Ft. Worth area and would like to attend, we'd love to have you join us.. Thanks for any help, David Armstrong 1) What is the default time period that the BDR waits when listening to LSA's from the DR before it decides that the DR is down and promotes itself to DR. All the literature we could find simply said that the BDR waits for the specified time period but never said what that period is. 2) In a Point-to-Point network in which the router in Area 0 is connected to FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and updates take place? From what we've found a DR and BDR is not elected in a strictly Point-to-Point network. I think an example would explain this question better: We have one 3620 router in our Ft. Worth office connected to an office in Houston (via FR), and office in Kansas City (via FR), an office in the DFW area (via ISDN) and the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and the firewall is connected to a 1720 going to the Internet. I'd like to implement OSPF on our network simply for the experience. However, I don't have 2 routers internally on our Ethernet LAN that can be configured
RE: Some OSPF Questions
Just to put in some empirical data, I set up two routers on an Ethernet link, in the classic OSPF broadcast scenario. Hello time is 10 seconds. Dead time 40 seconds ( 4xhello ) I determined which of the two routers was the DR, and which was the BDR I then plugged into and monitored from the BDR, using repeated "show ip ospf neighbor" commands I then unplugged the DR from the ethernet I then repeatedly reissued the show ip ospf neighbor commands I watched. The result of the show command was that the neighbor state FULL/DR remained in effect until the dead time was reached. After that, there was no neighbor. I also plugged it the first router back into the ethernet and repeatedly issued the commands. After a few seconds the first router showed up as a FULL/BDR Of some interest - the debug ip ospf hello and debug ip ospf events were silent immediately after unplugging the DR. It was only after the expiration of the dead time that debug ip ospf events indicated the election of a new DR, to whit, the router I was monitoring. Where this 0.5 second / half second thing comes from I cannot say. But using Cisco's defaults in a quick and dirty lab, it is safe to say that this is not what happens. Chuck -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Matthew Herman Sent: Friday, November 10, 2000 9:56 AM To: David Armstrong; [EMAIL PROTECTED] Subject: RE: Some OSPF Questions I'll throw my hat in.. 1. .5 seconds (50 msec) (Chapter 7, p142 exam cram acrc) 2. yes, there will be only one DR and its your single point of failure as well 8->. 3. doh...I have set up multiple as's on one router when I had multiple customer and redistributed into my AS. It worked ok but I am not saying that was a good way of configuring the router. 2/3 = 66 percent Still not enough to pass the ccie... matt -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of David Armstrong Sent: Friday, November 10, 2000 8:46 AM To: [EMAIL PROTECTED] Subject: Some OSPF Questions Last night at our BSCN study group meeting in Dallas we had some questions about OSPF that we weren't able to resolve. If someone or ones could answer these it would clarify some areas we're a little fuzzy on. Also, if you're iin the Dallas Ft. Worth area and would like to attend, we'd love to have you join us.. Thanks for any help, David Armstrong 1) What is the default time period that the BDR waits when listening to LSA's from the DR before it decides that the DR is down and promotes itself to DR. All the literature we could find simply said that the BDR waits for the specified time period but never said what that period is. 2) In a Point-to-Point network in which the router in Area 0 is connected to FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and updates take place? From what we've found a DR and BDR is not elected in a strictly Point-to-Point network. I think an example would explain this question better: We have one 3620 router in our Ft. Worth office connected to an office in Houston (via FR), and office in Kansas City (via FR), an office in the DFW area (via ISDN) and the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and the firewall is connected to a 1720 going to the Internet. I'd like to implement OSPF on our network simply for the experience. However, I don't have 2 routers internally on our Ethernet LAN that can be configured for Area 0 and elected to DR and BDR. All other routers connected to that router are via NBMA Point-to-Point connections. Since I only have one router on the Broadcast Multiaccess network (the 3620) and routers connected via PtoP don't participate in DR and BDR elections, how would updates occur? Can their only be one DR (in this case the 3620)? 3) The books and tutorials all state that "router ospf 6" defines ospf on the router with a process ID of 6. They then all say that you shouldn't define more than one process. Does that mean that you can have a router with the following: router ospf 6 network 10.100.0.0 0.0.255.255 router ospf 7 network 10.200.0.0 0.0.255.255 If this is an allowed configuration, what kind of instances would it be used for? Also, exactly what is the process ID used for? _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Some OSPF Questions
It appears that there might be some small misunderstanding about DR and BDR relationships. On a Multi-access net the DR is the "pseudonode" which represents the net. It is similar to NLSP in this regard. All OSPF routers refresh their LSAs occasionally. The DR sends LSA type 2 to all OSPF routers on the net. This way all routers get a refresh of who is who etc. Hellos are only used to establish and maintain adjacencies. Prior to 11.3 LSA's were sent every 30 minutes and all routers refreshed their databases. Now the default for all LSAs is 4 minutes(240 sec). This is configurable by using the command "timers lsa-group-pacing". A BDR, being an OSPF router would miss any other OSPF router after 10 times 4 = 40 secs using the default. This will cause it to change its routing behaviour, however the BDR to DR functionality would not take effect until it did not see the LSA type 2 packets from the DR after the set time(4 min default). I am not sure if that has been changed in 12.x the DR is the only router who originates LSA type 2 packets. Winston -Original Message- From: Frank B. [mailto:[EMAIL PROTECTED]] Sent: Saturday, November 11, 2000 1:24 AM To: David Armstrong; [EMAIL PROTECTED] Subject: Re: Some OSPF Questions You couldn't be more right! I jumped the gun. My response to your question 1) was incorrect. The BDR to Dr transition doesn't use the Hello protocol. The BDR listens to the LSAs from other routers (non-DR/BDRs) but doesn't reflood or ack them unless the DR fails to. I still can't find the exact timer value (or what it's called-if anything) that must go by before the BDR takes over. I've reviewed the RFC2328 section on flooding procedure and references to the DR/BDR, Doyle's, Thomas' and Caslow's book but no mention of the length of time. One response said 0.5 seconds and quoted an Exam Cram...I don't own any Exam Cram's but shouldn't there be a source reference somewhere? That very well could be correct but they had to get it from some where? Any ideas? Also, regarding question 3) Mr Berkowitz did come up with scenarios where he used multiple OSPF processes on one box. I'm sure there are enough possible permutations of networks, as well as IOS nerd knobs, out there that could support nearly anything. Generally speaking though I'd go with Cisco's guidance on this one...this practice is highly discouraged because it can take a toll on resources of the box. Just my opinion :) Thanks to all everyone out there willing to help.Frank David Armstrong wrote: > > Frank, > > Thanks for your response. It seems there is some confusion over the things > I'm confused about! :-) > > I appreciate your response. I've been looking at some of this as I could. I > do have a question about the BDR to DR promotion. We had found 2 sources > that said the BDR listens for LSA's from the DR rather than Hello packets. > That's really where the confusion came from. It would make sense that and > adjacency was formed between the DR and BDR and that the BDR would wait for > the Dead Interval before promoting to DR but both of these said that it > listened for LSA's. > > Do you know if this is correct? > > Thanks, > > David Armstrong > > -Original Message- > From: Frank B. [mailto:[EMAIL PROTECTED]] > Sent: November 10, 2000 1:49 PM > To: David Armstrong > Cc: [EMAIL PROTECTED] > Subject:Re: Some OSPF Questions > > David, > It appears you have received conflicting guidance on > your > question...I'll throw my 2 cents in but I hope I don't add > to the > confusion: > > 1) RouterDeadInterval is the legth of time a router waits > for a Hello > packet from a neighbor before declaring it down...the same > timer is used > by the BDR to determine whether the DR is down. The > RouterDeadInterval > is recommended by RFC 2328 to be "some multiple of the > HelloInterval > (say 4)" With respect to the HelloInterval RFC2328 states > "Sample value > for a local area network: 10 seconds." These are the > numbers Cisco's > implementation uses : 10 seconds for Hello and 40 seconds > for > RouterDead...for NBMA it's 30 and 120 respectively. > > 2) OSPF enabled routers maintain a data struture for each > OSPF enabled > interface. When you type "sh ip ospf int x" the router will > disply the >
Re: Some OSPF Questions
You couldn't be more right! I jumped the gun. My response to your question 1) was incorrect. The BDR to Dr transition doesn't use the Hello protocol. The BDR listens to the LSAs from other routers (non-DR/BDRs) but doesn't reflood or ack them unless the DR fails to. I still can't find the exact timer value (or what it's called-if anything) that must go by before the BDR takes over. I've reviewed the RFC2328 section on flooding procedure and references to the DR/BDR, Doyle's, Thomas' and Caslow's book but no mention of the length of time. One response said 0.5 seconds and quoted an Exam Cram...I don't own any Exam Cram's but shouldn't there be a source reference somewhere? That very well could be correct but they had to get it from some where? Any ideas? Also, regarding question 3) Mr Berkowitz did come up with scenarios where he used multiple OSPF processes on one box. I'm sure there are enough possible permutations of networks, as well as IOS nerd knobs, out there that could support nearly anything. Generally speaking though I'd go with Cisco's guidance on this one...this practice is highly discouraged because it can take a toll on resources of the box. Just my opinion :) Thanks to all everyone out there willing to help.Frank David Armstrong wrote: > > Frank, > > Thanks for your response. It seems there is some confusion over the things > I'm confused about! :-) > > I appreciate your response. I've been looking at some of this as I could. I > do have a question about the BDR to DR promotion. We had found 2 sources > that said the BDR listens for LSA's from the DR rather than Hello packets. > That's really where the confusion came from. It would make sense that and > adjacency was formed between the DR and BDR and that the BDR would wait for > the Dead Interval before promoting to DR but both of these said that it > listened for LSA's. > > Do you know if this is correct? > > Thanks, > > David Armstrong > > -Original Message- > From: Frank B. [mailto:[EMAIL PROTECTED]] > Sent: November 10, 2000 1:49 PM > To: David Armstrong > Cc: [EMAIL PROTECTED] > Subject:Re: Some OSPF Questions > > David, > It appears you have received conflicting guidance on > your > question...I'll throw my 2 cents in but I hope I don't add > to the > confusion: > > 1) RouterDeadInterval is the legth of time a router waits > for a Hello > packet from a neighbor before declaring it down...the same > timer is used > by the BDR to determine whether the DR is down. The > RouterDeadInterval > is recommended by RFC 2328 to be "some multiple of the > HelloInterval > (say 4)" With respect to the HelloInterval RFC2328 states > "Sample value > for a local area network: 10 seconds." These are the > numbers Cisco's > implementation uses : 10 seconds for Hello and 40 seconds > for > RouterDead...for NBMA it's 30 and 120 respectively. > > 2) OSPF enabled routers maintain a data struture for each > OSPF enabled > interface. When you type "sh ip ospf int x" the router will > disply the > contents of the data structure. Point-to-point interfaces > will NOT > display any DR or BDR--because there are none. With only 2 > routers on > the segment you don't need 'em. > > 3) I've never had a need to use 2 OSPF process but Someone > already > stated it being used to transition/migrate and that seems > reasonable...but keep in mind you'd have duplicate > everything! I would > imagine the strain on resources, say for the network to > synchronize, > would be enormous for larger networks. > > I hope this helps you out man...aloha, Frank > > David Armstrong wrote: > > > > Last night at our BSCN study group meeting in Dallas we > had some questions > > about OSPF that we weren't able to resolve. If someone or > ones could answer > > these it would clarify some areas we're a little fuzzy on. > Also, if you're > > iin the Dallas Ft. Worth area and would like to attend, > we'd love to have &
RE: Some OSPF Questions
On Fri, 10 Nov 2000, Matthew Herman wrote: > > >You ran OSPF to customers? So you were selling them transit and used > >OSPF? I imagine the evil a customer could do to your network if they had > > access to an OSPF neighbor router. > > I did not say it was bright. They had multiple T-1's and ospf allowed for > good load balancing without them having to get an AS. They learned routes > from me but I did not learn from them. That is pretty common I think. If both links were to you you can do load balacing without an IGP. You can also do eBGP multihop with a fake AS, that works well. Transit providers using IGP's these days to customers (like PSInet use to/still does use it to customers) is pretty much gone. Brian --- Brian Feeny, CCNP, CCDP [EMAIL PROTECTED] Network Administrator ShreveNet Inc. (ASN 11881) _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Some OSPF Questions
Ok.. This is getting good. Books are all over the place: Round two "The confusion continues". Question 1. I am quoting again from the exam cram acrc but its no bible either. "BDR IP Address: The backup for the DR. It waits for half a second to hear DR flooding updates. If the DR doesn't do its job, the BDR preempts and passes the updates to all adjacent routers. A new BDR is then elected." This sorta makes sense. When a router, say a third router, notices a change it tells the DR via mutlicast on 224.0.0.6, which then tells all the adjacent routers vial 224.0.0.5. The BDR is also listening on 224.0.0.6 is just not responding. However, if the DR does not send out the LSA, the BDR starts the work and send out LSA's to the adjacents. The time frame of .5 seconds makes sense. However, if the router that dies is the DR then it would make sense that it would take 4xhello to identify that the DR is gone. Question 2. >From the rfc(http://info.broker.isi.edu/in-notes/rfc/files/rfc2328.txt). So my read of this is you always have a DR. but exam cram acrc says that it not necessary in an nbma. So I would lean towards there is always DR it just might not be useful. For this example it's just not necessary because the whole concept of a DR-BDR is to minimize adjacencies but there is nobody to worry about. 7.3. The Designated Router Every broadcast and NBMA network has a Designated Router. The Designated Router performs two main functions for the routing protocol: The Designated Router originates a network-LSA on behalf of the network. The Designated Router becomes adjacent to all other routers on the network. Question 3. >You ran OSPF to customers? So you were selling them transit and used >OSPF? I imagine the evil a customer could do to your network if they had > access to an OSPF neighbor router. I did not say it was bright. They had multiple T-1's and ospf allowed for good load balancing without them having to get an AS. They learned routes from me but I did not learn from them. That is pretty common I think. -Original Message- From: Brian [mailto:[EMAIL PROTECTED]] Sent: Friday, November 10, 2000 11:28 AM To: Matthew Herman Cc: David Armstrong; [EMAIL PROTECTED] Subject: RE: Some OSPF Questions On Fri, 10 Nov 2000, Matthew Herman wrote: > I'll throw my hat in.. > > 1. .5 seconds (50 msec) (Chapter 7, p142 exam cram acrc) you sure you're not thinking of HSRP? > 2. yes, there will be only one DR and its your single point of failure as > well 8->. But not on PtP links, Their is no DR elected on a Point to Point link > 3. doh...I have set up multiple as's on one router when I had multiple > customer and redistributed into my AS. It worked ok but I am not saying > that was a good way of configuring the router. You ran OSPF to customers? So you were selling them transit and used OSPF? I imagine the evil a customer could do to your network if they had access to an OSPF neighbor router. Why not just static route to them as a stub? Brian > > 2/3 = 66 percent Still not enough to pass the ccie... > > matt > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of David > Armstrong > Sent: Friday, November 10, 2000 8:46 AM > To: [EMAIL PROTECTED] > Subject: Some OSPF Questions > > Last night at our BSCN study group meeting in Dallas we had some questions > about OSPF that we weren't able to resolve. If someone or ones could answer > these it would clarify some areas we're a little fuzzy on. Also, if you're > iin the Dallas Ft. Worth area and would like to attend, we'd love to have > you join us.. > > Thanks for any help, > > David Armstrong > > > 1) What is the default time period that the BDR waits when listening to > LSA's from the DR before it decides that the DR is down and promotes itself > to DR. All the literature we could find simply said that the BDR waits for > the specified time period but never said what that period is. > > 2) In a Point-to-Point network in which the router in Area 0 is connected to > FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and > updates take place? From what we've found a DR and BDR is not elected in a > strictly Point-to-Point network. > > I think an example would explain this question better: We have one 3620 > router in our Ft. Worth office connected to an office in Houston (via FR), > and office in Kansas City (via FR), an office in the DFW area (via ISDN) and > the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and the > firewall is connected to a 1720 going to the Internet. I'd like to implement > OSPF on our network simply for the experience
Re: Some OSPF Questions
At 9:49 AM -1000 11/10/2000, Frank B. wrote: > >3) I've never had a need to use 2 OSPF process but Someone already >stated it being used to transition/migrate and that seems >reasonable...but keep in mind you'd have duplicate everything! I would >imagine the strain on resources, say for the network to synchronize, >would be enormous for larger networks. Having multiple OSPF processes doesn't have to have a significant impact on resources, and, when used appropriately, may even decrease load. With two processes, assuming more than one area each, you will have an additional area 0.0.0.0 and a few unique tables, but, for the same number of links, the workload should be comparable in some areas and perhaps decreased in others. OSPF workload on a router has several major components. Maintaining neighbor and adjacency relationships, especially with short hello timers, can be substantial. The per-router load here is a function of the number of interfaces, the designated router status of each, and the timer settings. In other words, it is independent of the area size and depends purely on characteristics of the local router. The peak processing load often comes from the recomputation of the OSPF routing table, of which the Dijkstra algorithm is typically the most intensive part. Dijkstra proper deals with intra-area routes, while additional, more linear algorithms deal with inter-area and externals. For a single computation of the OSPF table, processing workload is proportional to: (number of intra-area routes * log(number of routers in area)) + number of inter-area routes seen in the area + number of external routes seen in the area The more frequent the computation, the greater the CPU load. The larger the internal size of the area, the greater the CPU load. So, if you can keep areas small, you reduce the probability that more than one area will need simultaneous Dijkstra computations. Something often forgotten is that while any given OSPF routing domain has one and only one area 0.0.0.0, there is no reason that you can't have multiple domains interconnected as a "backbone of backbones." I have used multiple OSPF processes for this purpose, as well as migration/consolidation (e.g., merging two enterprise networks). Most commonly, however, when I use a backbone of backbones, I have individual routers in single OSPF domains, but interconnect their ASBR's with static routes or BGP. For example, I've built intercontinental networks that variously had an area 0.0.0.0 for each continent, and/or for corporate headquarters. > > > 3) The books and tutorials all state that "router ospf 6" defines ospf on >> the router with a process ID of 6. They then all say that you shouldn't >> define more than one process. Does that mean that you can have a router with >> the following: >> >> router ospf 6 >>network 10.100.0.0 0.0.255.255 >> >> router ospf 7 >> network 10.200.0.0 0.0.255.255 >> >> If this is an allowed configuration, what kind of instances would it be used > > for? Also, exactly what is the process ID used for? >> _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Some OSPF Questions
David, It appears you have received conflicting guidance on your question...I'll throw my 2 cents in but I hope I don't add to the confusion: 1) RouterDeadInterval is the legth of time a router waits for a Hello packet from a neighbor before declaring it down...the same timer is used by the BDR to determine whether the DR is down. The RouterDeadInterval is recommended by RFC 2328 to be "some multiple of the HelloInterval (say 4)" With respect to the HelloInterval RFC2328 states "Sample value for a local area network: 10 seconds." These are the numbers Cisco's implementation uses : 10 seconds for Hello and 40 seconds for RouterDead...for NBMA it's 30 and 120 respectively. 2) OSPF enabled routers maintain a data struture for each OSPF enabled interface. When you type "sh ip ospf int x" the router will disply the contents of the data structure. Point-to-point interfaces will NOT display any DR or BDR--because there are none. With only 2 routers on the segment you don't need 'em. 3) I've never had a need to use 2 OSPF process but Someone already stated it being used to transition/migrate and that seems reasonable...but keep in mind you'd have duplicate everything! I would imagine the strain on resources, say for the network to synchronize, would be enormous for larger networks. I hope this helps you out man...aloha, Frank David Armstrong wrote: > > Last night at our BSCN study group meeting in Dallas we had some questions > about OSPF that we weren't able to resolve. If someone or ones could answer > these it would clarify some areas we're a little fuzzy on. Also, if you're > iin the Dallas Ft. Worth area and would like to attend, we'd love to have > you join us.. > > Thanks for any help, > > David Armstrong > > 1) What is the default time period that the BDR waits when listening to > LSA's from the DR before it decides that the DR is down and promotes itself > to DR. All the literature we could find simply said that the BDR waits for > the specified time period but never said what that period is. > > 2) In a Point-to-Point network in which the router in Area 0 is connected to > FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and > updates take place? From what we've found a DR and BDR is not elected in a > strictly Point-to-Point network. > > I think an example would explain this question better: We have one 3620 > router in our Ft. Worth office connected to an office in Houston (via FR), > and office in Kansas City (via FR), an office in the DFW area (via ISDN) and > the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and the > firewall is connected to a 1720 going to the Internet. I'd like to implement > OSPF on our network simply for the experience. However, I don't have 2 > routers internally on our Ethernet LAN that can be configured for Area 0 and > elected to DR and BDR. All other routers connected to that router are via > NBMA Point-to-Point connections. Since I only have one router on the > Broadcast Multiaccess network (the 3620) and routers connected via PtoP > don't participate in DR and BDR elections, how would updates occur? Can > their only be one DR (in this case the 3620)? > > 3) The books and tutorials all state that "router ospf 6" defines ospf on > the router with a process ID of 6. They then all say that you shouldn't > define more than one process. Does that mean that you can have a router with > the following: > > router ospf 6 > network 10.100.0.0 0.0.255.255 > > router ospf 7 > network 10.200.0.0 0.0.255.255 > > If this is an allowed configuration, what kind of instances would it be used > for? Also, exactly what is the process ID used for? > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Some OSPF Questions
On Fri, 10 Nov 2000, Matthew Herman wrote: > I'll throw my hat in.. > > 1. .5 seconds (50 msec) (Chapter 7, p142 exam cram acrc) you sure you're not thinking of HSRP? > 2. yes, there will be only one DR and its your single point of failure as > well 8->. But not on PtP links, Their is no DR elected on a Point to Point link > 3. doh...I have set up multiple as's on one router when I had multiple > customer and redistributed into my AS. It worked ok but I am not saying > that was a good way of configuring the router. You ran OSPF to customers? So you were selling them transit and used OSPF? I imagine the evil a customer could do to your network if they had access to an OSPF neighbor router. Why not just static route to them as a stub? Brian > > 2/3 = 66 percent Still not enough to pass the ccie... > > matt > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of David > Armstrong > Sent: Friday, November 10, 2000 8:46 AM > To: [EMAIL PROTECTED] > Subject: Some OSPF Questions > > Last night at our BSCN study group meeting in Dallas we had some questions > about OSPF that we weren't able to resolve. If someone or ones could answer > these it would clarify some areas we're a little fuzzy on. Also, if you're > iin the Dallas Ft. Worth area and would like to attend, we'd love to have > you join us.. > > Thanks for any help, > > David Armstrong > > > 1) What is the default time period that the BDR waits when listening to > LSA's from the DR before it decides that the DR is down and promotes itself > to DR. All the literature we could find simply said that the BDR waits for > the specified time period but never said what that period is. > > 2) In a Point-to-Point network in which the router in Area 0 is connected to > FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and > updates take place? From what we've found a DR and BDR is not elected in a > strictly Point-to-Point network. > > I think an example would explain this question better: We have one 3620 > router in our Ft. Worth office connected to an office in Houston (via FR), > and office in Kansas City (via FR), an office in the DFW area (via ISDN) and > the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and the > firewall is connected to a 1720 going to the Internet. I'd like to implement > OSPF on our network simply for the experience. However, I don't have 2 > routers internally on our Ethernet LAN that can be configured for Area 0 and > elected to DR and BDR. All other routers connected to that router are via > NBMA Point-to-Point connections. Since I only have one router on the > Broadcast Multiaccess network (the 3620) and routers connected via PtoP > don't participate in DR and BDR elections, how would updates occur? Can > their only be one DR (in this case the 3620)? > > 3) The books and tutorials all state that "router ospf 6" defines ospf on > the router with a process ID of 6. They then all say that you shouldn't > define more than one process. Does that mean that you can have a router with > the following: > > router ospf 6 > network 10.100.0.0 0.0.255.255 > > router ospf 7 > network 10.200.0.0 0.0.255.255 > > If this is an allowed configuration, what kind of instances would it be used > for? Also, exactly what is the process ID used for? > > > > > _ > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > --- Brian Feeny, CCNP, CCDP [EMAIL PROTECTED] Network Administrator ShreveNet Inc. (ASN 11881) _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Some OSPF Questions
On Fri, 10 Nov 2000, David Armstrong wrote: > Last night at our BSCN study group meeting in Dallas we had some questions > about OSPF that we weren't able to resolve. If someone or ones could answer > these it would clarify some areas we're a little fuzzy on. Also, if you're > iin the Dallas Ft. Worth area and would like to attend, we'd love to have > you join us.. > > Thanks for any help, > > David Armstrong > > > 1) What is the default time period that the BDR waits when listening to > LSA's from the DR before it decides that the DR is down and promotes itself > to DR. All the literature we could find simply said that the BDR waits for > the specified time period but never said what that period is. This is the "dead interval", which is 4 times the hello interval, which is 40 seconds (hello interval is 10 seconds). > > 2) In a Point-to-Point network in which the router in Area 0 is connected to > FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and > updates take place? From what we've found a DR and BDR is not elected in a > strictly Point-to-Point network. Their is no DR/BDR for that link, but the routers do become adjacent. BDR/DR is not something that is a "necessity" for something like OSPF to operate...it is elected so that every router doesn't send LSA's to every router, to calm that sort of madness. All that is required for routers to exchange LSA's is that they become adjacent. Routers on PtP links always become adjacent (barring any misconfiguration). > > 3) The books and tutorials all state that "router ospf 6" defines ospf on > the router with a process ID of 6. They then all say that you shouldn't > define more than one process. Does that mean that you can have a router with > the following: > > router ospf 6 > network 10.100.0.0 0.0.255.255 > > router ospf 7 > network 10.200.0.0 0.0.255.255 > > If this is an allowed configuration, what kind of instances would it be used > for? Also, exactly what is the process ID used for? The above is legal, but you need area statments on the end of those network statments. I have no idea why anyone would want to do this however. Brian > > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > --- Brian Feeny, CCNP, CCDP [EMAIL PROTECTED] Network Administrator ShreveNet Inc. (ASN 11881) _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Some OSPF Questions
Comments inserted below. >1) What is the default time period that the BDR waits when listening to >LSA's from the DR before it decides that the DR is down and promotes itself >to DR. All the literature we could find simply said that the BDR waits for >the specified time period but never said what that period is. As per the various OSPF rfc's (2328 for ospfv2), the bdr will wait out the RouterDeadInterval before assuming the role of DR. Generally, this period is set to 4 times the hello interval (in Cisco and Juniper from what I recall) which is usually 10 seconds. Hence, 40 seconds would be the delay in this case. >2) In a Point-to-Point network in which the router in Area 0 is connected to >FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and >updates take place? From what we've found a DR and BDR is not elected in a >strictly Point-to-Point network. Your findings are correct. A DR/BDR is only elected in Broadcast or NBMA networks It should be noted that DR's and BDRs simply represent multiaccess segments with summary LSA's (type 2). These summaries are very much like type 1 lsa's which all routers can and will generate. Overall the convergence process is handled by the flooding of appropriate LSAs. > >3) The books and tutorials all state that "router ospf 6" defines ospf on >the router with a process ID of 6. They then all say that you shouldn't >define more than one process. Does that mean that you can have a router with >the following: > >router ospf 6 > network 10.100.0.0 0.0.255.255 > >router ospf 7 > network 10.200.0.0 0.0.255.255 > >If this is an allowed configuration, what kind of instances would it be used >for? Also, exactly what is the process ID used for? > Cisco does support the running of multiple, exclusive ospf processes on one router. The process ID is a locally significant value that separates these processes within the router. Very few situations justify the use of multiple processes. The only few I've seen all entailed migrations where this setup was a intermediary stage. Hope this helps. Pete _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Some OSPF Questions
I'll throw my hat in.. 1. .5 seconds (50 msec) (Chapter 7, p142 exam cram acrc) 2. yes, there will be only one DR and its your single point of failure as well 8->. 3. doh...I have set up multiple as's on one router when I had multiple customer and redistributed into my AS. It worked ok but I am not saying that was a good way of configuring the router. 2/3 = 66 percent Still not enough to pass the ccie... matt -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of David Armstrong Sent: Friday, November 10, 2000 8:46 AM To: [EMAIL PROTECTED] Subject: Some OSPF Questions Last night at our BSCN study group meeting in Dallas we had some questions about OSPF that we weren't able to resolve. If someone or ones could answer these it would clarify some areas we're a little fuzzy on. Also, if you're iin the Dallas Ft. Worth area and would like to attend, we'd love to have you join us.. Thanks for any help, David Armstrong 1) What is the default time period that the BDR waits when listening to LSA's from the DR before it decides that the DR is down and promotes itself to DR. All the literature we could find simply said that the BDR waits for the specified time period but never said what that period is. 2) In a Point-to-Point network in which the router in Area 0 is connected to FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and updates take place? From what we've found a DR and BDR is not elected in a strictly Point-to-Point network. I think an example would explain this question better: We have one 3620 router in our Ft. Worth office connected to an office in Houston (via FR), and office in Kansas City (via FR), an office in the DFW area (via ISDN) and the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and the firewall is connected to a 1720 going to the Internet. I'd like to implement OSPF on our network simply for the experience. However, I don't have 2 routers internally on our Ethernet LAN that can be configured for Area 0 and elected to DR and BDR. All other routers connected to that router are via NBMA Point-to-Point connections. Since I only have one router on the Broadcast Multiaccess network (the 3620) and routers connected via PtoP don't participate in DR and BDR elections, how would updates occur? Can their only be one DR (in this case the 3620)? 3) The books and tutorials all state that "router ospf 6" defines ospf on the router with a process ID of 6. They then all say that you shouldn't define more than one process. Does that mean that you can have a router with the following: router ospf 6 network 10.100.0.0 0.0.255.255 router ospf 7 network 10.200.0.0 0.0.255.255 If this is an allowed configuration, what kind of instances would it be used for? Also, exactly what is the process ID used for? _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Some OSPF Questions
Last night at our BSCN study group meeting in Dallas we had some questions about OSPF that we weren't able to resolve. If someone or ones could answer these it would clarify some areas we're a little fuzzy on. Also, if you're iin the Dallas Ft. Worth area and would like to attend, we'd love to have you join us.. Thanks for any help, David Armstrong 1) What is the default time period that the BDR waits when listening to LSA's from the DR before it decides that the DR is down and promotes itself to DR. All the literature we could find simply said that the BDR waits for the specified time period but never said what that period is. 2) In a Point-to-Point network in which the router in Area 0 is connected to FR, ISDN, X.25 or ATM branch offices (networks), how does convergence and updates take place? From what we've found a DR and BDR is not elected in a strictly Point-to-Point network. I think an example would explain this question better: We have one 3620 router in our Ft. Worth office connected to an office in Houston (via FR), and office in Kansas City (via FR), an office in the DFW area (via ISDN) and the owner's home (via ISDN). The 3620 is behind a firewall (Pix 520) and the firewall is connected to a 1720 going to the Internet. I'd like to implement OSPF on our network simply for the experience. However, I don't have 2 routers internally on our Ethernet LAN that can be configured for Area 0 and elected to DR and BDR. All other routers connected to that router are via NBMA Point-to-Point connections. Since I only have one router on the Broadcast Multiaccess network (the 3620) and routers connected via PtoP don't participate in DR and BDR elections, how would updates occur? Can their only be one DR (in this case the 3620)? 3) The books and tutorials all state that "router ospf 6" defines ospf on the router with a process ID of 6. They then all say that you shouldn't define more than one process. Does that mean that you can have a router with the following: router ospf 6 network 10.100.0.0 0.0.255.255 router ospf 7 network 10.200.0.0 0.0.255.255 If this is an allowed configuration, what kind of instances would it be used for? Also, exactly what is the process ID used for? _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
