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]> 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]>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]] >> *Sent:* November-23-10 8:25 PM >> *To:* 'David Betz'; '[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]] *On Behalf Of *David Betz >> *Sent:* November-23-10 7:32 PM >> *To:* [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
