RE: Ospf Router ID Manual Router ID? [7:32056]
It sure helps to "nail-down" the router-id when playing around with DR/BDR elections or with virtual-links (since you point to the router-id) I believe that bootcamp lab #1 has some gotchas that refer to router-id issues. Not that I spent a ton of time (grin) getting this lab to work only to find out my problem was with how the routers selected their router id's. Ever since then, I like to manual tell the box what router id to use. Did that help? btw, it saves time in pounding your head against the desk because your labs don't work. Also, is router really your last name? Tim -Original Message- From: Steve Router [mailto:[EMAIL PROTECTED]] Sent: Tuesday, January 15, 2002 3:14 PM To: [EMAIL PROTECTED] Subject: Ospf Router ID Manual Router ID? Does any one know if assigning the Router ID's in Ospf helps out in ospf or save any time...??? _ Join the worlds largest e-mail service with MSN Hotmail. http://www.hotmail.com **Note: CCIE Security list is available. For more information go to: http://www.groupstudy.com/list/security.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32056&t=32056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ospf router id vs loop back [7:32022]
At 12:44 PM -0500 1/15/02, Chuck Larrieu wrote: >interesting question. came up in a customer meeting the other day as well. > >IMHO, this gets down to design preference. Agreed. As you suggest, there's art as well as science here. >I am of the school of thought >that there needs be some way of getting to any router in a network ( design >permitting, cost permitting ), and that each router in a network needs some >unique and easily identified pneumonic. > >So IMHO, one should use loopbacks, numbered according to some rational >scheme, and that those "routes" should be advertised.IMHO This should be >true, no matter what routing protocol you are using. > >However, others will ask whether in a 5000 router domain, you want 5000 >extra routes in your tables. That is a valid counterargument. If you have that many routers, you presumably have a hierarchical design with summarization. Using Cisco's conservative number of routers per OSPF area, allocate 128 addresses, as part of an aggregatable block, per area. This gives 39+ blocks. If one assumes stubby areas, you'd get a maximum of 128 additional routes per nonzero area, plus 40 extra routes in area 0.0.0.0. 40 areas, however, is a lot for a single OSPF domain. When I've dealt with networks of this size, I've separated them into multiple OSPF domains linked by a backbone of backbones, either BGP or statically routed. That backbone of backbones, of course, gives the potential for additional aggregation. > >Using the RID command under the OSPF process, you can set up a rational >identification scheme. The RID does not necessarily have to be related to >interface numbering. But then you have the issue of correlating RIDs to the >addresses one actually uses to get to the router in question, making it a >bit more complicated to find things when you need to. That's why I like the RID to be the "address of last resort" to reach the router. > >JMHO. > >Chuck > > > > >""john smith"" wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... >> Hi, >> Is there reason one would prefer loopback address for router ID when using >> Ospf over the router id command that can be used under "router ospf " and >> vice versa. Is there a need to advertise the router IDs in OSPF. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32048&t=32022 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ospf router id vs loop back [7:32022]
interesting question. came up in a customer meeting the other day as well. IMHO, this gets down to design preference. I am of the school of thought that there needs be some way of getting to any router in a network ( design permitting, cost permitting ), and that each router in a network needs some unique and easily identified pneumonic. So IMHO, one should use loopbacks, numbered according to some rational scheme, and that those "routes" should be advertised.IMHO This should be true, no matter what routing protocol you are using. However, others will ask whether in a 5000 router domain, you want 5000 extra routes in your tables. That is a valid counterargument. Using the RID command under the OSPF process, you can set up a rational identification scheme. The RID does not necessarily have to be related to interface numbering. But then you have the issue of correlating RIDs to the addresses one actually uses to get to the router in question, making it a bit more complicated to find things when you need to. JMHO. Chuck ""john smith"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi, > Is there reason one would prefer loopback address for router ID when using > Ospf over the router id command that can be used under "router ospf " and > vice versa. Is there a need to advertise the router IDs in OSPF. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=32025&t=32022 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF Router ID and IP Addresses [7:24003]
So it is important to use loop interface in OSPF, because it is always
up.-
I recently discovered that the "shutdown" command works on loopback
interfaces also. ;->
Chuck
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Li Hou
Sent: Saturday, October 27, 2001 10:53 AM
To: [EMAIL PROTECTED]
Subject: Re: OSPF Router ID and IP Addresses [7:24003]
Of course the 193.x.x.x will become the routers' ID after reboot.
If you start OSPF before the interface Eth 2 up, then the ID should keep the
last one until reboot!
So it is important to use loop interface in OSPF, because it is always up.
""Thompson, Robert D"" P4HkO{O"PBNE
:[EMAIL PROTECTED]
> Hi All,
>
> Can anybody clear something up for me.
>
> In OSPF when selecting the Router ID, what Interface will OSPF choose as
the
> Router ID on this particular router. For example
>
> Interface Ethernet 0
> IP address 10.1.1.1 255.0.0.0
>
> Interface Ethernet 1
> IP address 172.16.100.1 255.255.0.0
>
> Interface Ethernet 2
> IP address 193.221.200.1 255.255.255.0
>
> rest of config not listed for this discussion and IP address structure
made
> up for the discussion
>
>
> (in this case I won't use a loopback interface, purely to discuss Router
ID
> and IP address considerations)
>
> I understand its the highest IP address that will win, in this case will
it
> be 10.1.1.1? or will it be 193.221.200.1
>
> I will appreciate any comments
>
> Cheers
>
> Rob
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Re: OSPF Router ID and IP Addresses [7:24003]
Of course the 193.x.x.x will become the routers' ID after reboot.
If you start OSPF before the interface Eth 2 up, then the ID should keep the
last one until reboot!
So it is important to use loop interface in OSPF, because it is always up.
""Thompson, Robert D"" P4HkO{O"PBNE
:[EMAIL PROTECTED]
> Hi All,
>
> Can anybody clear something up for me.
>
> In OSPF when selecting the Router ID, what Interface will OSPF choose as
the
> Router ID on this particular router. For example
>
> Interface Ethernet 0
> IP address 10.1.1.1 255.0.0.0
>
> Interface Ethernet 1
> IP address 172.16.100.1 255.255.0.0
>
> Interface Ethernet 2
> IP address 193.221.200.1 255.255.255.0
>
> rest of config not listed for this discussion and IP address structure
made
> up for the discussion
>
>
> (in this case I won't use a loopback interface, purely to discuss Router
ID
> and IP address considerations)
>
> I understand its the highest IP address that will win, in this case will
it
> be 10.1.1.1? or will it be 193.221.200.1
>
> I will appreciate any comments
>
> Cheers
>
> Rob
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Re: OSPF Router ID and IP Addresses [7:24003]
Robert, It would select 193.221.200.1 as its highest router id. IP addresses set on Lopopbacks gets more preferance than the interfaces. ie.,if the loopback is set with an ip addrs, then the physical interfaces and their ip addrs are ignored nor will they participate on the router-id election. thanks Suresh CNE,MCSE+I,CLP,CCSA,CCNA,MCNS,CCNP _ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=24026&t=24003 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID and IP Addresses [7:24003]
Alternatively, you can use the 'router-id x.x.x.x' command to force a router ID http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/113ed_cr/n p1_r/1rospf.htm#xtocid2457225 Though I find it easier to use a single loopback for the OSPF process. > Robert, > > If your trying to find out what the RID will be on that box, try doing a "sh > ip ospf" and it should tell you. That aside. In your config, since you > don't have any loopbacks (as you stated you know those ip's will be selected > first as the RID) it'll take the highest ip of active interfaces (whether or > not they're in the ospf domain). So in your example, it'll start at the > first octet and choose the highest. That being 193.221.200.1 > > I think it's safe to make up a little list. > > 1) Highest IP of any loopback on the box > 2) highest ip of any interface (in ospf or not) > > Tim > > > > -Original Message- > > From: Thompson, Robert D [SMTP:[EMAIL PROTECTED]] > > Sent: Wednesday, October 24, 2001 6:50 AM > > To: [EMAIL PROTECTED] > > Subject: OSPF Router ID and IP Addresses [7:24003] > > > > Hi All, > > > > Can anybody clear something up for me. > > > > In OSPF when selecting the Router ID, what Interface will OSPF choose as > > the > > Router ID on this particular router. For example > > > > Interface Ethernet 0 > > IP address 10.1.1.1 255.0.0.0 > > > > Interface Ethernet 1 > > IP address 172.16.100.1 255.255.0.0 > > > > Interface Ethernet 2 > > IP address 193.221.200.1 255.255.255.0 > > > > rest of config not listed for this discussion and IP address structure > > made > > up for the discussion > > > > > > (in this case I won't use a loopback interface, purely to discuss Router > > ID > > and IP address considerations) > > > > I understand its the highest IP address that will win, in this case will > > it > > be 10.1.1.1? or will it be 193.221.200.1 > > > > I will appreciate any comments > > > > Cheers > > > > Rob Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=24010&t=24003 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF Router ID and IP Addresses [7:24003]
Router choose Numerically highest ip address as it ID.. In this case I think
it will be 193.221.200.1
If the router is configured with a loopback address then it would be given
priority... I think once the router has chosen its router ID then it stay
fixed..
Murali
-Original Message-
From: Thompson, Robert D [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, October 24, 2001 2:50 PM
To: [EMAIL PROTECTED]
Subject: OSPF Router ID and IP Addresses [7:24003]
Hi All,
Can anybody clear something up for me.
In OSPF when selecting the Router ID, what Interface will OSPF choose as the
Router ID on this particular router. For example
Interface Ethernet 0
IP address 10.1.1.1 255.0.0.0
Interface Ethernet 1
IP address 172.16.100.1 255.255.0.0
Interface Ethernet 2
IP address 193.221.200.1 255.255.255.0
rest of config not listed for this discussion and IP address structure made
up for the discussion
(in this case I won't use a loopback interface, purely to discuss Router ID
and IP address considerations)
I understand its the highest IP address that will win, in this case will it
be 10.1.1.1? or will it be 193.221.200.1
I will appreciate any comments
Cheers
Rob
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Re: OSPF Router ID [7:25]
Router ID sequence in ospf 1) Loopback IP address, 2) No loopback address configured, router will choose the numerically highest IP address on any of its Physical interface, as long the interface is up. Hope this help Vincent ""Larry Ogun-Banjo"" ? [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I saw something confusing about OSPF Router ID which I haven't checked out but I > thought if its true, it could be a brain teaser during the BSCN exam > According to the official BSCN documentation, the router ID takes on the highest > IP address. > But according to another training document, if you have a loopback address > configured, the router ID is the lowest active address on the router. > Does anyone know if this is true and why the addresses would change? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=25&t=25 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
>I thought you did. Since it's highly possible that the version of >English language I studied at school is different from yours, we just >simply don't understand each other. However, since you newer know who >your reader is, stating the rules as short as possible is always a good >idea. In this particular case I would say "RID is numerically highest >addresss on a loopback interface, if there are any loopbacks, and >numerically highest address on an active physical or subinterface >otherwise". Well stated. > >BTW, if we are still talking about ciscos, the above statement is true >only for the takeoff situation. At flight you can add/delete loopbacks, >this won't change the RID. Unfortunately, I don't have enough spares to >check what happens if you delete the RID-defining loopback on the >router, then create a RID-defining loopback with the same address on the >other router and then launch OSPF on it. Historically, at least when I set up scenarios in around IOS 11.1, things break. OSPF will refuse to create a neighbor relationship with another router with the same router ID. In the scenario you describe, until you restart OSPF on the first router, the router ID will persist. I'm in the process of working with a new virtual lab as well as CertificationZone, and duplicate router ID, I'm sure will be in some of the troubleshooting scenarios. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
Delete your loopback, reload the router and tell us how well your virtual links work. :) -- Eric Fairfield CCIE #6413 "Oleg Mazurov" <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > "Howard C. Berkowitz" wrote: > > > > >"Howard C. Berkowitz" wrote: > > >> > > >> > > The latter is wrong. The order of selection is: > > >> >> > > >> >> 1. Numerically highest IP addresss on a loopback interface, when > > >> >> there are multiple loopback addresses. > > >> >> > > >> >> 2. IP address on the loopback address when only a single loopback > > >> >>is defined. > > >> >> > > >> >> 3. Numerically highest IP address on an active physical (or > > >> >>logical other than > > >> >> loopback address)--active as in no shutdown > > >> > > > >> >I have a strong feeling that p.2 doesn't make any sense. > > >> > > >> Point 2 should read "on the loopback interface" Is that your concern? > > >> > > > > > >When only a single loopback interface is defined, it's address is the > > >highest of available loopback addresses, right? > > > > > >BTW, p.1 is wrong for ciscos. When multiple IP addresses are defined on > > >a loopback interface, OSPF takes only primary address of it and ignores > > >the secondaries. > > > > Who said anything about secondary addresses? > > > > I thought you did. Since it's highly possible that the version of > English language I studied at school is different from yours, we just > simply don't understand each other. However, since you newer know who > your reader is, stating the rules as short as possible is always a good > idea. In this particular case I would say "RID is numerically highest > addresss on a loopback interface, if there are any loopbacks, and > numerically highest address on an active physical or subinterface > otherwise". > > BTW, if we are still talking about ciscos, the above statement is true > only for the takeoff situation. At flight you can add/delete loopbacks, > this won't change the RID. Unfortunately, I don't have enough spares to > check what happens if you delete the RID-defining loopback on the > router, then create a RID-defining loopback with the same address on the > other router and then launch OSPF on it. > > /felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
"Howard C. Berkowitz" wrote: > > >"Howard C. Berkowitz" wrote: > >> > >> > > The latter is wrong. The order of selection is: > >> >> > >> >> 1. Numerically highest IP addresss on a loopback interface, when > >> >> there are multiple loopback addresses. > >> >> > >> >> 2. IP address on the loopback address when only a single loopback > >> >>is defined. > >> >> > >> >> 3. Numerically highest IP address on an active physical (or > >> >>logical other than > >> >> loopback address)--active as in no shutdown > >> > > >> >I have a strong feeling that p.2 doesn't make any sense. > >> > >> Point 2 should read "on the loopback interface" Is that your concern? > >> > > > >When only a single loopback interface is defined, it's address is the > >highest of available loopback addresses, right? > > > >BTW, p.1 is wrong for ciscos. When multiple IP addresses are defined on > >a loopback interface, OSPF takes only primary address of it and ignores > >the secondaries. > > Who said anything about secondary addresses? > I thought you did. Since it's highly possible that the version of English language I studied at school is different from yours, we just simply don't understand each other. However, since you newer know who your reader is, stating the rules as short as possible is always a good idea. In this particular case I would say "RID is numerically highest addresss on a loopback interface, if there are any loopbacks, and numerically highest address on an active physical or subinterface otherwise". BTW, if we are still talking about ciscos, the above statement is true only for the takeoff situation. At flight you can add/delete loopbacks, this won't change the RID. Unfortunately, I don't have enough spares to check what happens if you delete the RID-defining loopback on the router, then create a RID-defining loopback with the same address on the other router and then launch OSPF on it. /felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
>"Howard C. Berkowitz" wrote: >> >> > > The latter is wrong. The order of selection is: >> >> >> >> 1. Numerically highest IP addresss on a loopback interface, when >> >> there are multiple loopback addresses. >> >> >> >> 2. IP address on the loopback address when only a single loopback >> >>is defined. >> >> >> >> 3. Numerically highest IP address on an active physical (or >> >>logical other than >> >> loopback address)--active as in no shutdown >> > >> >I have a strong feeling that p.2 doesn't make any sense. >> >> Point 2 should read "on the loopback interface" Is that your concern? >> > >When only a single loopback interface is defined, it's address is the >highest of available loopback addresses, right? > >BTW, p.1 is wrong for ciscos. When multiple IP addresses are defined on >a loopback interface, OSPF takes only primary address of it and ignores >the secondaries. Who said anything about secondary addresses? The P1 case: int loop 0 ip addr 192.168.1.1 255.255.255.0 int loop 1 ip addr 192.168.3.1 255.255.255.0 int loop 2 ip addr 192.168.2.1 255.255.255.0 The router id will be 192.168.3.1 > >/felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
this thread is cracking me up! but you're tossing up some good questions, and hopefully, you're learning how the OSPF router ID is assigned. The statement from p.1 is multiple *loopback* interfaces, not multiple *addresses* on a loopback interface; using the following scenario as an example interface loopback 0 ip address 172.16.1.1 255.255.248.0 interface loopback 1 ip address 172.16.200.1 255.255.248.0 interface ethernet 0 ip address 192.168.5.1 255.255.255.0 interface serial 0 ip address 192.168.10.1 255.255.255.252 (No mention of secondaries, although your point is likely correct and well taken) thus in this scenario, the loopback 1 address would become the OSPF router ID because its IP address is higher than loopback 0, even though the physical interfaces have higher IP addresses, because OSPF prefers the *highest numbered loopback address* if loopback 1 did not exist, loopback 0 address would become the OSPF router ID because OSPF prefers *loopback over physical* interfaces for router ID, even though the physical interfaces have higher addresses if neither loopback existed, serial 0 address would become the OSPF router ID because it has the highest IP address capiche? LOL... dazed, amazed and amused on a Friday vacation-day -e- - Original Message - From: "Oleg Mazurov" <[EMAIL PROTECTED]> Newsgroups: groupstudy.cisco To: <[EMAIL PROTECTED]> Sent: Friday, April 06, 2001 9:20 AM Subject: Re: OSPF Router ID > "Howard C. Berkowitz" wrote: > > > > > > The latter is wrong. The order of selection is: > > >> > > >> 1. Numerically highest IP addresss on a loopback interface, when > > >> there are multiple loopback addresses. > > >> > > >> 2. IP address on the loopback address when only a single loopback > > >>is defined. > > >> > > >> 3. Numerically highest IP address on an active physical (or > > >>logical other than > > >> loopback address)--active as in no shutdown > > > > > >I have a strong feeling that p.2 doesn't make any sense. > > > > Point 2 should read "on the loopback interface" Is that your concern? > > > > When only a single loopback interface is defined, it's address is the > highest of available loopback addresses, right? > > BTW, p.1 is wrong for ciscos. When multiple IP addresses are defined on > a loopback interface, OSPF takes only primary address of it and ignores > the secondaries. > > /felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
I believe Howard is stating in p.1 that if you have multiple loopback interfaces the highest addressed interface is chosen. Not secondaries. -- Eric Fairfield CCIE #6413 "Oleg Mazurov" <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > "Howard C. Berkowitz" wrote: > > > > > > The latter is wrong. The order of selection is: > > >> > > >> 1. Numerically highest IP addresss on a loopback interface, when > > >> there are multiple loopback addresses. > > >> > > >> 2. IP address on the loopback address when only a single loopback > > >>is defined. > > >> > > >> 3. Numerically highest IP address on an active physical (or > > >>logical other than > > >> loopback address)--active as in no shutdown > > > > > >I have a strong feeling that p.2 doesn't make any sense. > > > > Point 2 should read "on the loopback interface" Is that your concern? > > > > When only a single loopback interface is defined, it's address is the > highest of available loopback addresses, right? > > BTW, p.1 is wrong for ciscos. When multiple IP addresses are defined on > a loopback interface, OSPF takes only primary address of it and ignores > the secondaries. > > /felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
"Howard C. Berkowitz" wrote: > > > > The latter is wrong. The order of selection is: > >> > >> 1. Numerically highest IP addresss on a loopback interface, when > >> there are multiple loopback addresses. > >> > >> 2. IP address on the loopback address when only a single loopback > >>is defined. > >> > >> 3. Numerically highest IP address on an active physical (or > >>logical other than > >> loopback address)--active as in no shutdown > > > >I have a strong feeling that p.2 doesn't make any sense. > > Point 2 should read "on the loopback interface" Is that your concern? > When only a single loopback interface is defined, it's address is the highest of available loopback addresses, right? BTW, p.1 is wrong for ciscos. When multiple IP addresses are defined on a loopback interface, OSPF takes only primary address of it and ignores the secondaries. /felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
OK, I'm sorry. I had been grown by mathematicians. Anyway, if p.2 does make sense to you, p.4 would have to be added, describing the situation when only one active non-loopback interface exists. /felis John Neiberger wrote: > > It makes perfect sense. Let me rephrase the rules and we'll see if that > clears up the issue. > > If you have no loopback interfaces configured, the router ID will be > the highest IP address on an active interface. > > If you have a single loopback address configured, the router ID will > take that IP address regardless of whether or not it is higher or lower > than other active IP addresses on the router. > > If you have multiple loopback interfaces configured, the router ID will > be the highest IP address on any loopback interface. > > >>> "Oleg Mazurov" <[EMAIL PROTECTED]> 4/6/01 8:50:30 AM >>> > > The latter is wrong. The order of selection is: > > > > 1. Numerically highest IP addresss on a loopback interface, when > > there are multiple loopback addresses. > > > > 2. IP address on the loopback address when only a single loopback is > defined. > > > > 3. Numerically highest IP address on an active physical (or logical > other than > > loopback address)--active as in no shutdown > > I have a strong feeling that p.2 doesn't make any sense. > > /felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
> > The latter is wrong. The order of selection is: >> >> 1. Numerically highest IP addresss on a loopback interface, when >> there are multiple loopback addresses. >> >> 2. IP address on the loopback address when only a single loopback >>is defined. >> >> 3. Numerically highest IP address on an active physical (or >>logical other than >> loopback address)--active as in no shutdown > >I have a strong feeling that p.2 doesn't make any sense. Point 2 should read "on the loopback interface" Is that your concern? > >/felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
It makes perfect sense. Let me rephrase the rules and we'll see if that clears up the issue. If you have no loopback interfaces configured, the router ID will be the highest IP address on an active interface. If you have a single loopback address configured, the router ID will take that IP address regardless of whether or not it is higher or lower than other active IP addresses on the router. If you have multiple loopback interfaces configured, the router ID will be the highest IP address on any loopback interface. >>> "Oleg Mazurov" <[EMAIL PROTECTED]> 4/6/01 8:50:30 AM >>> > The latter is wrong. The order of selection is: > > 1. Numerically highest IP addresss on a loopback interface, when > there are multiple loopback addresses. > > 2. IP address on the loopback address when only a single loopback is defined. > > 3. Numerically highest IP address on an active physical (or logical other than > loopback address)--active as in no shutdown I have a strong feeling that p.2 doesn't make any sense. /felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
> The latter is wrong. The order of selection is: > > 1. Numerically highest IP addresss on a loopback interface, when > there are multiple loopback addresses. > > 2. IP address on the loopback address when only a single loopback is defined. > > 3. Numerically highest IP address on an active physical (or logical other than > loopback address)--active as in no shutdown I have a strong feeling that p.2 doesn't make any sense. /felis _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
>I saw something confusing about OSPF Router ID which I haven't >checked out but I >thought if its true, it could be a brain teaser during the BSCN exam >According to the official BSCN documentation, the router ID takes on >the highest >IP address. >But according to another training document, if you have a loopback address >configured, the router ID is the lowest active address on the router. >Does anyone know if this is true and why the addresses would change? The latter is wrong. The order of selection is: 1. Numerically highest IP addresss on a loopback interface, when there are multiple loopback addresses. 2. IP address on the loopback address when only a single loopback is defined. 3. Numerically highest IP address on an active physical (or logical other than loopback address)--active as in no shutdown -- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** Howard C. Berkowitz [EMAIL PROTECTED] Technical Director, CertificationZone.com Senior Mgr. IP Protocols & Algorithms, Advanced Technology Investments, NortelNetworks (for ID only) "retired" Certified Cisco Systems Instructor (CID) #93005 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
1) Set RouterID using the Router-ID command 2) Highest Loopback IP address 3) If no Loopback then the Highest ACTIVE IP address Eric Fairfield CCIE #6413 ""Vincent"" <[EMAIL PROTECTED]> wrote in message 9ak9oe$d1n$[EMAIL PROTECTED]">news:9ak9oe$d1n$[EMAIL PROTECTED]... > Router ID sequence in ospf > > 1) Loopback IP address, > > 2) No loopback address configured, router will choose the numerically > highest IP address on any of its > Physical interface, as long the interface is up. > > Hope this help > Vincent > > > > ""Larry Ogun-Banjo"" <[EMAIL PROTECTED]> ? > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > I saw something confusing about OSPF Router ID which I haven't checked out > but I > > thought if its true, it could be a brain teaser during the BSCN exam > > According to the official BSCN documentation, the router ID takes on the > highest > > IP address. > > But according to another training document, if you have a loopback address > > configured, the router ID is the lowest active address on the router. > > Does anyone know if this is true and why the addresses would change? _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF Router ID
The confusion may come from the RFC which says : Router ID A 32-bit number that uniquely identifies this router in the AS. One possible implementation strategy would be to use the smallest IP interface address belonging to the router. But if you are going for a Cisco exam, make sure to answer the what Vincent describe below. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Vincent Sent: Friday, April 06, 2001 12:24 PM To: [EMAIL PROTECTED] Subject: Re: OSPF Router ID Router ID sequence in ospf 1) Loopback IP address, 2) No loopback address configured, router will choose the numerically highest IP address on any of its Physical interface, as long the interface is up. Hope this help Vincent ""Larry Ogun-Banjo"" <[EMAIL PROTECTED]> ? [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I saw something confusing about OSPF Router ID which I haven't checked out but I > thought if its true, it could be a brain teaser during the BSCN exam > According to the official BSCN documentation, the router ID takes on the highest > IP address. > But according to another training document, if you have a loopback address > configured, the router ID is the lowest active address on the router. > Does anyone know if this is true and why the addresses would change? _ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID
Router ID sequence in ospf 1) Loopback IP address, 2) No loopback address configured, router will choose the numerically highest IP address on any of its Physical interface, as long the interface is up. Hope this help Vincent ""Larry Ogun-Banjo"" <[EMAIL PROTECTED]> ? [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I saw something confusing about OSPF Router ID which I haven't checked out but I > thought if its true, it could be a brain teaser during the BSCN exam > According to the official BSCN documentation, the router ID takes on the highest > IP address. > But according to another training document, if you have a loopback address > configured, the router ID is the lowest active address on the router. > Does anyone know if this is true and why the addresses would change? _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID/Loopback interface
Inorder to reflect the new router ID without rebooting ,You can shutdown your serial 2/1 interface and then bring it up by no shutdown. Thangavel - Original Message - From: Erick B. <[EMAIL PROTECTED]> To: Louie Belt <[EMAIL PROTECTED]>; 'Ejay Hire' <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Wednesday, October 18, 2000 5:22 PM Subject: RE: OSPF Router ID/Loopback interface > Some minor corrections. > > The OSPF process will use the *highest* loopback IP > address if a loopback interface is configured. > Otherwise, it uses the *highest* IP address on a > physical interface. To configure OSPF (router ospf x) > you need a interface with IP to be in a up/up state. > > You can reboot to have the router ID reflected or you > can remove the OSPF process and add it back. > > --- Louie Belt <[EMAIL PROTECTED]> wrote: > > It will take the loopback address as it's ID, even > > if it is not the highest > > IP address on the router. Loopbacks take precedence > > over higher IP's with > > respect to Router ID's for OSPF. You will have to > > reboot your router for > > this change to be reflected. Once an ID is chosen, > > it will keep that ID > > regardless of changes until the router is rebooted. > > > > Louie > > > > > > > > > > -Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED]]On Behalf Of > > Ejay Hire > > Sent: Wednesday, October 18, 2000 1:50 PM > > To: [EMAIL PROTECTED]; [EMAIL PROTECTED] > > Subject: Re: OSPF Router ID/Loopback interface > > > > > > No, It's the highest Ip on the router. > > > > > > Original Message Follows > > From: "John Deatherage" <[EMAIL PROTECTED]> > > Reply-To: "John Deatherage" <[EMAIL PROTECTED]> > > To: <[EMAIL PROTECTED]> > > Subject: OSPF Router ID/Loopback interface > > Date: Wed, 18 Oct 2000 11:15:27 -0700 > > > > If I add a loopback interface to a router, when will > > the router take it as > > the router ID? Here's a scenario: > > > > Serial2/1 is the current router ID: 209.1.1.1 > > > > I add Loopback0, which is 10.0.0.1 > > > > Shouldn't the router take this as its router ID? > > When does this happen? > > Doing: > > > > clear ip ospf process > > > > Still shows the old router ID. Is there any way to > > force the router to take > > the ID from the loopback interface? On another > > router, I couldn't get it to > > change until after reload. > > > > _ > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to > > [EMAIL PROTECTED] > > > > > _ > > Get Your Private, Free E-mail from MSN Hotmail at > > http://www.hotmail.com. > > > > Share information about yourself, create your own > > public profile at > > http://profiles.msn.com. > > > > _ > > 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] > > > __ > Do You Yahoo!? > Yahoo! Messenger - Talk while you surf! It's FREE. > http://im.yahoo.com/ > > _ > 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: OSPF Router ID/Loopback interface
Some minor corrections. The OSPF process will use the *highest* loopback IP address if a loopback interface is configured. Otherwise, it uses the *highest* IP address on a physical interface. To configure OSPF (router ospf x) you need a interface with IP to be in a up/up state. You can reboot to have the router ID reflected or you can remove the OSPF process and add it back. --- Louie Belt <[EMAIL PROTECTED]> wrote: > It will take the loopback address as it's ID, even > if it is not the highest > IP address on the router. Loopbacks take precedence > over higher IP's with > respect to Router ID's for OSPF. You will have to > reboot your router for > this change to be reflected. Once an ID is chosen, > it will keep that ID > regardless of changes until the router is rebooted. > > Louie > > > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]On Behalf Of > Ejay Hire > Sent: Wednesday, October 18, 2000 1:50 PM > To: [EMAIL PROTECTED]; [EMAIL PROTECTED] > Subject: Re: OSPF Router ID/Loopback interface > > > No, It's the highest Ip on the router. > > > Original Message Follows > From: "John Deatherage" <[EMAIL PROTECTED]> > Reply-To: "John Deatherage" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Subject: OSPF Router ID/Loopback interface > Date: Wed, 18 Oct 2000 11:15:27 -0700 > > If I add a loopback interface to a router, when will > the router take it as > the router ID? Here's a scenario: > > Serial2/1 is the current router ID: 209.1.1.1 > > I add Loopback0, which is 10.0.0.1 > > Shouldn't the router take this as its router ID? > When does this happen? > Doing: > > clear ip ospf process > > Still shows the old router ID. Is there any way to > force the router to take > the ID from the loopback interface? On another > router, I couldn't get it to > change until after reload. > > _ > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to > [EMAIL PROTECTED] > > _ > Get Your Private, Free E-mail from MSN Hotmail at > http://www.hotmail.com. > > Share information about yourself, create your own > public profile at > http://profiles.msn.com. > > _ > 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] __ Do You Yahoo!? Yahoo! Messenger - Talk while you surf! It's FREE. http://im.yahoo.com/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF Router ID/Loopback interface
It will take the loopback address as it's ID, even if it is not the highest IP address on the router. Loopbacks take precedence over higher IP's with respect to Router ID's for OSPF. You will have to reboot your router for this change to be reflected. Once an ID is chosen, it will keep that ID regardless of changes until the router is rebooted. Louie -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Ejay Hire Sent: Wednesday, October 18, 2000 1:50 PM To: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: Re: OSPF Router ID/Loopback interface No, It's the highest Ip on the router. Original Message Follows From: "John Deatherage" <[EMAIL PROTECTED]> Reply-To: "John Deatherage" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Subject: OSPF Router ID/Loopback interface Date: Wed, 18 Oct 2000 11:15:27 -0700 If I add a loopback interface to a router, when will the router take it as the router ID? Here's a scenario: Serial2/1 is the current router ID: 209.1.1.1 I add Loopback0, which is 10.0.0.1 Shouldn't the router take this as its router ID? When does this happen? Doing: clear ip ospf process Still shows the old router ID. Is there any way to force the router to take the ID from the loopback interface? On another router, I couldn't get it to change until after reload. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your own public profile at http://profiles.msn.com. _ 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: OSPF Router ID/Loopback interface
No, It's the highest Ip on the router. Original Message Follows From: "John Deatherage" <[EMAIL PROTECTED]> Reply-To: "John Deatherage" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Subject: OSPF Router ID/Loopback interface Date: Wed, 18 Oct 2000 11:15:27 -0700 If I add a loopback interface to a router, when will the router take it as the router ID? Here's a scenario: Serial2/1 is the current router ID: 209.1.1.1 I add Loopback0, which is 10.0.0.1 Shouldn't the router take this as its router ID? When does this happen? Doing: clear ip ospf process Still shows the old router ID. Is there any way to force the router to take the ID from the loopback interface? On another router, I couldn't get it to change until after reload. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your own public profile at http://profiles.msn.com. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Router ID/Loopback interface
John, It depends on which IOS version you use. In later images you will need to either reboot or to remove the process and readd it. I do not quite remember when this behavior changed. Rgds, Patrick John Deatherage wrote: > If I add a loopback interface to a router, when will the router take it as > the router ID? Here's a scenario: > > Serial2/1 is the current router ID: 209.1.1.1 > > I add Loopback0, which is 10.0.0.1 > > Shouldn't the router take this as its router ID? When does this happen? > Doing: > > clear ip ospf process > > Still shows the old router ID. Is there any way to force the router to take > the ID from the loopback interface? On another router, I couldn't get it to > change until after reload. > > _ > 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]
