Yes, you set the Hub as the DR because it is the only one with a full mesh to the others. As for the advantage of broadcast type over NBMA, two that I can think of. 1. You don't need neighbor statements (but you do need the broadcast on your frame maps). 2. Faster timers
As for your neighbors below, did you have neighbor statements on R4 and R5? You only have to have the neighbor statement on one side to bring up the relationship. On Fri, Jul 22, 2011 at 7:01 AM, Alef <[email protected]> wrote: > So i am playing around with OSPF. FR cloud with a hub, R2 and neighbors R4, > R5 and R6. > No adjacencies are formed yet. I add some neighbors on the hub. No ospf > network types are defined, normal NBMA FR cloud. > > Below is what happened when i add neighbors, remove them again, and the ospf > adjacencies keep forming despite that these are not configured on the hub > anymore. Not until the ospf network type broadcast is defined they really > don't come up anymore. Does this has something to do with the DR (maybe R2, > didn't check) still has a link-state database and communicates it back to the > neighbors. If so, wouldn't that be some violation of RFC? Doesn't seem right > if i remove the neighbors they still come up! Is there some purge time for it > to be removed from the database? > > Some questions: > -Why do we have to set the hub to be the DR? Is it because the hub is the one > who has a full mesh to all the pvc's and the others don't ? > -And what is the benefit of setting it to the ip ospf network broadcast > statement over say nbma ? A DR gets elected on broadcast network type as well. > > Regards, > Alef > > R2(config-if)#router ospf 1 > R2(config-router)#neighbor 150.50.255.4 > R2(config-router)#neighbor 150.50.255.5 > R2(config-router)#neighbor 150.50.255.6 > R2(config-router)#do sh ip ospf neigh > > Neighbor ID Pri State Dead Time Address Interface > N/A 0 ATTEMPT/DROTHER 00:01:47 150.50.255.4 Serial0/1/0 > N/A 0 ATTEMPT/DROTHER 00:01:48 150.50.255.5 Serial0/1/0 > N/A 0 ATTEMPT/DROTHER 00:01:50 150.50.255.6 Serial0/1/0 > R2(config-router)# > Jul 22 11:41:25.194: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.4.4 on Serial0/1/0 > from LOADING to FULL, Loading Done > Jul 22 11:41:25.290: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.5.5 on Serial0/1/0 > from LOADING to FULL, Loading Done > Jul 22 11:41:25.290: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.6.6 on Serial0/1/0 > from LOADING to FULL, Loading Done > > Ok. Now i remove the adjacencies. > > R2(config-router)#no neighbor 150.50.255.4 > R2(config-router)#no neighbor 150.50.255.5 > R2(config-router)#no neighbor 150.50.255.5 > Jul 22 11:41:44.274: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.4.4 on Serial0/1/0 > from FULL to DOWN, Neighbor Down: Neighbor deconfigured > R2(config-router)#no neighbor 150.50.255.6 > R2(config-router)# > Jul 22 11:41:45.614: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.5.5 on Serial0/1/0 > from FULL to DOWN, Neighbor Down: Neighbor deconfigured > R2(config-router)# > Jul 22 11:41:46.922: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.6.6 on Serial0/1/0 > from FULL to DOWN, Neighbor Down: Neighbor deconfigured > > R2(config-router)#do sh ip ospf neigh > > No more neighbors. Great. > > R2(config-router)#do sh ip ospf neigh > Jul 22 11:41:58.706: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.5.5 on Serial0/1/0 > from LOADING to FULL, Loading Done > Jul 22 11:41:58.786: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.4.4 on Serial0/1/0 > from LOADING to FULL, Loading Done > R2(config-router)#do sh ip ospf neigh > > Neighbor ID Pri State Dead Time Address Interface > 150.50.4.4 1 FULL/DROTHER 00:01:58 150.50.255.4 Serial0/1/0 > 150.50.5.5 1 FULL/DR 00:01:58 150.50.255.5 Serial0/1/0 > R2(config-router)#do sh ip ospf neigh > > Neighbor ID Pri State Dead Time Address Interface > 150.50.4.4 1 FULL/DROTHER 00:01:58 150.50.255.4 Serial0/1/0 > 150.50.5.5 1 FULL/DR 00:01:58 150.50.255.5 Serial0/1/0 > R2(config-router)# > Jul 22 11:42:04.322: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.6.6 on Serial0/1/0 > from LOADING to FULL, Loading Done > R2(config-router)#do sh ip ospf neigh > > Neighbor ID Pri State Dead Time Address Interface > 150.50.4.4 1 FULL/DROTHER 00:01:58 150.50.255.4 Serial0/1/0 > 150.50.5.5 1 FULL/DROTHER 00:01:58 150.50.255.5 Serial0/1/0 > 150.50.6.6 1 FULL/DR 00:01:57 150.50.255.6 Serial0/1/0 > > What? They are back again. Let me clear the OSPF process. > R2(config-router)#do clear ip ospf proc > Reset ALL OSPF processes? [no]: y > R2(config-router)# > Jul 22 11:42:16.086: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.4.4 on Serial0/1/0 > from FULL to DOWN, Neighbor Down: Interface down or detached > Jul 22 11:42:16.086: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.5.5 on Serial0/1/0 > from FULL to DOWN, Neighbor Down: Interface down or detached > Jul 22 11:42:16.086: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.6.6 on Serial0/1/0 > from FULL to DOWN, Neighbor Down: Interface down or detached > R2(config-router)#do sh ip ospf neigh > > Neighbor ID Pri State Dead Time Address Interface > 150.50.4.4 1 2WAY/DROTHER 00:01:31 150.50.255.4 Serial0/1/0 > 150.50.5.5 1 2WAY/DROTHER 00:01:33 150.50.255.5 Serial0/1/0 > 150.50.6.6 1 2WAY/DROTHER 00:01:38 150.50.255.6 Serial0/1/0 > R2(config-router)# > > And back they are again. I did this twice. > Jul 22 11:44:16.106: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.4.4 on Serial0/1/0 > from LOADING to FULL, Loading Done > Jul 22 11:44:16.146: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.5.5 on Serial0/1/0 > from LOADING to FULL, Loading Done > Jul 22 11:44:16.178: %OSPF-5-ADJCHG: Process 1, Nbr 150.50.6.6 on Serial0/1/0 > from LOADING to FULL, Loading Done > R2(config-router)#do clear ip ospf proc > Reset ALL OSPF processes? [no]: y > <snip> > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
