too much ospf neighbor adjecencies between two routers

[YANGCCIE4]

Hey guys,

I am looking into our netowrk ospf configuration. I found there are too much adjecenies between two of our network routers.these adjecencies are upon the defferent vlans. for example:

c2#sh ip os nei  | i 10.40.111

10.40.111.6       1   FULL/DROTHER    00:00:36    10.1.152.11     Vlan672

10.40.111.2       1   FULL/DROTHER    00:00:37    10.40.147.4     Vlan147

10.40.111.6       1   FULL/BDR        00:00:38    10.40.147.2     Vlan147

10.40.111.2       1   FULL/DROTHER    00:00:32    10.40.146.4     Vlan146

10.40.111.6       1   FULL/BDR        00:00:35    10.40.146.2     Vlan146

10.40.111.6      40   FULL/DR         00:00:37    10.40.45.2      Vlan455

10.40.111.10      1   FULL/BDR        00:00:31    10.40.6.6       GigabitEthernet4/28

10.40.111.6       1   FULL/BDR        00:00:39    10.40.245.26    Vlan115

10.40.111.6       1   FULL/BDR        00:00:39    10.40.245.18    Vlan114

10.40.111.6       1   FULL/BDR        00:00:39    10.40.245.10    Vlan113

10.40.111.6       1   FULL/BDR        00:00:39    10.40.246.2     Vlan198

10.40.111.6       1   FULL/BDR        00:00:30    10.40.245.2     Vlan197

10.40.111.6       1   FULL/BDR        00:00:37    10.40.244.2     Vlan196

10.40.111.11      1   FULL/BDR        00:00:31    10.40.4.150     Vlan4

10.40.111.6       1   FULL/DROTHER    00:00:37    10.40.4.2       Vlan4

10.40.111.6       1   FULL/BDR        00:00:37    64.142.175.2    Vlan175

10.40.111.6       1   FULL/BDR        00:00:37    64.142.132.226  Vlan160

10.40.111.6       1   FULL/BDR        00:00:38    10.188.0.2      Vlan590

10.40.111.6       1   FULL/BDR        00:00:31    10.40.13.2      Vlan13

you will see there are too many adjecencies on 10.40.111.6 (one router),

I think once a while these adjecencies will exchange the OSPF DB/Hello/KeepAlive packats between each other.

will this affect the performance of the router ? why dont we just keep one management vlan adjecency and keep the rest vlan by passive-interface ?

i am looking for  some optimizing solution or suggestions.

thanks

[Richard Burts · Accepted solution]

There may be an argument for a second neighbor adjacency between two routers since it allows the routers to remain neighbors in one interface is having a problem. But beyond that multiple adjacencies causes the router to do more work (sending and tracking keepalive messages, flooding LSAs, etc) with very little benefit.

You already have identified the best optimizing command - passive-interface.

HTH

Rick

[acampbell · Accepted solution]

Hi,

You need to know your network
Which VLANS need to propgate routing updates and therefore
need to form OSPF neighborships.

Lets say in your case

GigabitEthernet4/28
VLAN 146
VLAN 147

!
router ospf 1
passive interface default
no passive-interface int g4/28
no passive-interface int vlan 146
no passive-interface int vlan 147
network xxxxxxxxx etc
etc
!

HTH
Alex

[YANGCCIE4]

your asumption is correct. but my concern is since we only need one or two adjecencies to exchange the ospf packets. we dont need so many interface to keep sending keep alive between these two routers. maybe we can passive-interface most of all the svi except the management or the transit svi.

right ?

thanks Alex.

[YANGCCIE4]

Rick, I think we are in the same page,

Thanks your response !