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Home > Archive > CCNP > April 2002 > DR/BDR question
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| SurfinUSA 2002-04-26, 3:39 pm |
| Guys, I just read where you have a DR and a BDR for every network in an area, which tells me you can have more than one DR/BDR for a given area. My question is: How do the routers that join the network know which DR/BDR is for them? I mean, since its layer 3, couldnt potentially any of the DR/BDRs in the network be for them? OR will it select the DR/BDR on the network its on? for example, if it has a 172.16.10.1 ip address say for E0, does that mean it will find other routers only on 172.16.10.0 network? This may sound confusing, but Im somewhat confused myself at the moment about it. Any insight? | |
| mikeghet 2002-04-26, 4:52 pm |
| I am not completly sure but I think it is becasue all the routers know which area they are in. Then I think after that they determine the dr/bdr baed on the ips in that area. | |
| SurfinUSA 2002-04-26, 7:37 pm |
| Here is a direct cut and paste on what I read. See if this makes any more sense to you guys: "Note: DRs and BDRs are elected on a per-network basis. An OSPF area can contain more than one IP network, so each area can (and usually does) have multiple DRs and BDRs." | |
| wirechild 2002-04-26, 10:12 pm |
| Don't confuse Area with Network. Only one network can have a DR and BDR but an area could be made up of several networks. This is one of those reasons to use contiguous networks within an area, because when you have several areas it gets really hard to manage where the DR's will be if any at all. The ABR's are the most important router in any OSPF network.... |
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