Essentially, right now, if I were asked a question on the written that required me to know this, then I'm stuck. I can totally see Cisco showing me a scenario and a config snippet and asking something like "If "network 10.0.0.0" is entered on R2 2700ms after it is entered on R1, who is the BDR?" (then show 5 routers) Is 2700ms within the time that R2 will wait for R1 or not? Obviously, if R1 takes too long, it will miss the election.
On Wed, Nov 24, 2010 at 8:53 AM, David Betz <[email protected]> wrote: > The results are not in question, the timing is. > > My current theory is that election is always from the list of routers that > a rouer has a two-way relationship with, thus the question has nothing to do > with that and needs to be pushed back to: "How long does a router wait to > collect two-way state neighbors before stop waiting and starting and > election?" > > > On Wed, Nov 24, 2010 at 5:14 AM, Jason Maynard > <[email protected]>wrote: > >> I have not read all the comments but I thought I would try this >> >> >> >> I configured OSPF on a single router and ran “debug ip ospf adja” >> >> >> >> >> >> *Mar 1 00:01:07.091: OSPF: Interface FastEthernet0/0 going Up >> >> *Mar 1 00:01:07.595: OSPF: Build router LSA for area 0, router ID >> 1.1.1.1, seq 0x80000001 >> >> *Mar 1 00:01:47.091: OSPF: end of Wait on interface FastEthernet0/0 >> >> *Mar 1 00:01:47.091: OSPF: DR/BDR election on FastEthernet0/0 >> >> *Mar 1 00:01:47.095: OSPF: Elect BDR 1.1.1.1 >> >> *Mar 1 00:01:47.095: OSPF: Elect DR 1.1.1.1 >> >> *Mar 1 00:01:47.099: OSPF: Elect BDR 0.0.0.0 >> >> *Mar 1 00:01:47.099: OSPF: Elect DR 1.1.1.1 >> >> *Mar 1 00:01:47.103: DR: 1.1.1.1 (Id) BDR: none >> >> *Mar 1 00:01:47.603: OSPF: No full nbrs to build Net Lsa for interface >> FastEthernet0/0 >> >> >> >> Does this help? >> >> >> >> >> >> >> >> *From:* [email protected] [mailto: >> [email protected]] *On Behalf Of *David Betz >> *Sent:* November-24-10 3:37 AM >> >> *To:* [email protected] >> *Subject:* Re: [OSL | CCIE_RS] OSPF Election Time >> >> >> >> That's my current theory. However, this really shouldn't be a theory, but >> scientific fact. I've looked at the RFC and still haven't found anything. >> Granted, it was a skim. I'd need to scan it to be sure of >> it's absence or presence. >> >> On Wed, Nov 24, 2010 at 2:10 AM, antonio <[email protected]> >> wrote: >> >> Maybe you have to look at wait timer (by default equals to dead-interval) >> >> regards >> antonio >> >> Il 24/11/2010 03:43, David Betz ha scritto: >> >> Upon closer examination of the process, it seems that DR/BDR election is >> based on the candidates that are adjacencies (neighbor routers with >> priority > 0). Thus, the question is pushed backed a step: when does a >> router say "I've 2-way with n-number of routers on this broadcast >> segment, let's begin election."? Even then, multiple routers are doing >> this, but given that that is per-segment, the election results should be >> the same all over. So, that part shouldn't be an issue. >> >> On Tue, Nov 23, 2010 at 7:58 PM, David Betz <[email protected] >> >> <mailto:[email protected]>> wrote: >> >> Yes? >> >> I've done this experiment myriad times and looked over the data for >> a long time. What is your personal analysis of this data? Any >> conclusion? I've not been any to come up with with anything based >> on this data. If we are going to do our work off empirical data, we >> need to have a series of tests with a specified baseline. However, >> I'm more looking for an axiom from the [seemingly non-existent] >> documentation. Normally I'd look at the RFC, but do not any any >> reason to think that Cisco is following it at this point. >> >> >> On Tue, Nov 23, 2010 at 7:49 PM, Jason Maynard >> >> <[email protected] <mailto:[email protected]>> wrote: >> >> Have a look at the times below. Between two routers in a >> broadcast network >> >> *Mar 1 00:09:00.215: OSPF: end of Wait on interface >> FastEthernet0/0 >> >> *Mar 1 00:09:00.215: OSPF: DR/BDR election on FastEthernet0/0 >> >> *Mar 1 00:09:00.219: OSPF: Elect BDR 222.222.222.222 >> >> *Mar 1 00:09:00.219: OSPF: Elect DR 222.222.222.222 >> >> *Mar 1 00:09:00.223: OSPF: Elect BDR 0.0.0.0 >> >> *Mar 1 00:09:00.223: OSPF: Elect DR 222.222.222.222 >> >> *Mar 1 00:09:00.227: DR: 222.222.222.222 (Id) BDR: none >> >> *Mar 1 00:09:00.323: OSPF: 2 Way Communication to 1.1.1.1 on >> FastEthernet0/0, state 2WAY >> >> *Mar 1 00:09:00.323: OSPF: Neighbor change Event on interface >> FastEthernet0/0 >> >> *Mar 1 00:09:00.327: OSPF: DR/BDR election on FastEthernet0/0 >> >> *Mar 1 00:09:00.327: OSPF: Elect BDR 1.1.1.1 >> >> *Mar 1 00:09:00.331: OSPF: Elect DR 222.222.222.222 >> >> *Mar 1 00:09:00.331: DR: 222.222.222.222 (Id) BDR: >> 1.1.1.1 (Id) >> >> *Mar 1 00:09:00.331: OSPF: Send DBD to 1.1.1.1 on >> FastEthernet0/0 seq 0xA62 opt 0x52 flag 0x7 len 32 >> >> *Mar 1 00:09:00.331: OSPF: Neighbor change Event on interface >> FastEthernet0/0 >> >> *Mar 1 00:09:00.331: OSPF: DR/BDR election on FastEthernet0/0 >> >> *Mar 1 00:09:00.331: OSPF: Elect BDR 1.1.1.1 >> >> *Mar 1 00:09:00.331: OSPF: Elect DR 222.222.222.222 >> >> *Mar 1 00:09:00.331: DR: 222.222.222.222 (Id) BDR: >> 1.1.1.1 (Id) >> >> *Mar 1 00:09:00.331: OSPF: Neighbor change Event on interface >> FastEthernet0/0 >> >> *Mar 1 00:09:00.331: OSPF: DR/BDR election on FastEthernet0/0 >> >> *Mar 1 00:09:00.331: OSPF: Elect BDR 1.1.1.1 >> >> *Mar 1 00:09:00.331: OSPF: Elect DR 222.222.222.222 >> >> *Mar 1 00:09:00.331: DR: 222.222.222.222 (Id) BDR: >> 1.1.1.1 (Id) >> >> *Mar 1 00:09:00.331: OSPF: Rcv DBD from 1.1.1.1 on >> FastEthernet0/0 seq 0x1376 opt 0x52 flag 0x7 len 32 mtu 1500 >> state EXSTART >> >> *Mar 1 00:09:00.331: OSPF: First DBD and we are not SLAVE >> >> *Mar 1 00:09:00.379: OSPF: Rcv DBD from 1.1.1.1 on >> FastEthernet0/0 seq 0xA62 opt 0x52 flag 0x2 len 52 mtu 1500 >> state EXSTART >> >> *Mar 1 00:09:00.383: OSPF: NBR Negotiation Done. We are the MASTER >> >> *Mar 1 00:09:00.387: OSPF: Send DBD to 1.1.1.1 on >> FastEthernet0/0 seq 0xA63 opt 0x52 flag 0x3 len 52 >> >> *Mar 1 00:09:00.475: OSPF: Rcv DBD from 1.1.1.1 on >> FastEthernet0/0 seq 0xA63 opt 0x52 flag 0x0 len 32 mtu 1500 >> state EXCHANGE >> >> *Mar 1 00:09:00.479: OSPF: Send DBD to 1.1.1.1 on >> FastEthernet0/0 seq 0xA64 opt 0x52 flag 0x1 len 32 >> >> *Mar 1 00:09:00.483: OSPF: Send LS REQ to 1.1.1.1 length 12 LSA >> count 1 >> >> *Mar 1 00:09:00.567: OSPF: Rcv LS REQ from 1.1.1.1 on >> FastEthernet0/0 length 36 LSA count 1 >> >> *Mar 1 00:09:00.571: OSPF: Send UPD to 10.0.0.2 on >> FastEthernet0/0 length 40 LSA count 1 >> >> *Mar 1 00:09:00.619: OSPF: Rcv DBD from 1.1.1.1 on >> FastEthernet0/0 seq 0xA64 opt 0x52 flag 0x0 len 32 mtu 1500 >> state EXCHANGE >> >> *Mar 1 00:09:00.623: OSPF: Exchange Done with 1.1.1.1 on >> FastEthernet0/0 >> >> *Mar 1 00:09:00.623: OSPF: Rcv LS UPD from 1.1.1.1 on >> FastEthernet0/0 length 64 LSA count 1 >> >> *Mar 1 00:09:00.627: OSPF: Synchronized with 1.1.1.1 on >> FastEthernet0/0, state FULL >> >> *Mar 1 00:09:00.631: %OSPF-5-ADJCHG: Process 1, Nbr 1.1.1.1 on >> FastEthernet0/0 from LOADING to FULL, Loading Done >> >> *Mar 1 00:09:00.727: OSPF: Build network LSA for >> FastEthernet0/0, router ID 222.222.222.222 >> >> *Mar 1 00:09:00.731: OSPF: Build network LSA for >> FastEthernet0/0, router ID 222.222.222.222 >> >> *Mar 1 00:09:00.735: OSPF: Build router LSA for area 0, router >> ID 222.222.222.222, seq 0x80000004 >> >> *Mar 1 00:09:03.439: OSPF: Rcv LS UPD from 1.1.1.1 on >> FastEthernet0/0 length 64 LSA count 1 >> >> *From:*Jason Maynard [mailto:[email protected] >> <mailto:[email protected]>] >> *Sent:* November-23-10 8:25 PM >> *To:* 'David Betz'; '[email protected] >> >> <mailto:[email protected]>' >> >> >> *Subject:* RE: [OSL | CCIE_RS] OSPF Election Time >> >> Well that depends >> >> How long does the device take to boot up compared to other devices >> >> When is the device ready to participate in the OSPF election >> process (running more services on a device may take it longer to >> start participating compared to a router with less services) >> >> DR and BDR election is done via the Hello protocol – >> >> OSPF Network Type | Hello | DR/BDR | >> _________________________________________ >> Broadcast | 10sec | Elects DR/BDR| >> _________________________________________ >> NonBroadcast | 30sec | Elects DR/BDR| >> _________________________________________ >> P2MP | 30sec | No DR/BDR | >> _________________________________________ >> P2MP NonBroadcast | 30sec | No DR/BDR | >> _________________________________________ >> P2P | 10sec | No DR/BDR | >> >> If you want to control which devices become the DR/BDR you can >> use “*ip ospf priority” and set all devices that you do not want >> to be DR/BDR to “0” *** >> >> Not sure exactly how may hellos before the DR/BDR election takes >> place, perhaps I will lab it up to see - >> >> HTH >> >> *From:*[email protected] >> <mailto:[email protected]> >> [mailto:[email protected] >> <mailto:[email protected]>] *On Behalf Of >> *David Betz >> *Sent:* November-23-10 7:32 PM >> *To:* [email protected] >> >> <mailto:[email protected]> >> >> >> *Subject:* [OSL | CCIE_RS] OSPF Election Time >> >> I've not been able to figure this out nor can I find any >> documentation for this: how long does OSPF wait for others to >> cast their vote before doing the DR/BDR election? >> >> If R1, R2, and R3 come online with 10.1.1.X/25 (X=RX) ip >> addresses, and R1 and R2 see each other's messages, they will >> start an election. If R3 is there, it wins... if it's too late, >> R2 wins. >> >> When is "too late"? >> >> >> >> >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com >> >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com >> >> >> > >
_______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
