HELP!!! routers wont form neighbours

hello there..

I am trying to set up a single area OSPF routing network but BB1 and R1 (see picture and PT file below) wont form neighbors in other to exchange route information. Other routers in the network are working fine and exchanging routes.

I have checked, and both mentioned routers are in the same area (area 0) and have both link ends in the same subnet. Why they have refused to exchange routes is beyond me.

Someone please troubleshoot and let me know what's wrong. I would also love to know how to use the debug command: debug ip ospf adj.

please find below the configuration of both routers in question.

BB1
hostname BB1
...
interface FastEthernet0/0
ip address 172.16.10.254 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 172.16.11.254 255.255.255.0
duplex auto
speed auto
!
interface Serial0/0/0
ip address 10.1.1.100 255.255.255.0
....
!
router ospf 1
log-adjacency-changes
network 10.1.1.0 0.0.0.255 area 0
network 172.16.0.0 0.0.255.255 area 0
!
ip classless

R1
!
hostname R1
...
interface Serial0/0/0
ip address 192.168.1.17 255.255.255.240
clock rate 64000
!
interface Serial0/1/0
ip address 192.168.1.33 255.255.255.240
clock rate 64000
!
interface Serial0/2/0
ip address 192.168.1.49 255.255.255.240
clock rate 64000
!
interface Serial0/3/0
ip address 10.1.1.1 255.255.255.0
clock rate 64000
...
router ospf 1
log-adjacency-changes
network 10.1.1.1 0.0.0.0 area 0
network 192.168.0.0 0.0.255.255 area 0
...
end

troubleshoot.JPG

Find more posts tagged with

Free for TechExams community: Cybersecurity salary guide

Compare cert salaries and plan your next career move

Button

Comments

networker050184

Is the interface up? Can you ping across?

How you use the debug is just type in the command.

RouteMyPacket

On R1 under the OSPF process, do the following and see what you get

router ospf 1
no network 10.1.1.1 0.0.0.0 area 0
network 10.1.1.0 0.0.0.255 area 0

[Deleted User]

Have you tried a show cdp neighbors, show ip ospf border-routers, or show ip ospf? Post those configs here.

MAC_Addy

Oh, RouteMyPacket, you beat me to it.

networker050184

RouteMyPacket wrote: »

On R1 under the OSPF process, do the following and see what you get

router ospf 1
no network 10.1.1.1 0.0.0.0 area 0
network 10.1.1.0 0.0.0.255 area 0

That doesn't matter. As long as it matches the interface it's fine. It is actually my preferred method to always use a 0.0.0.0 mask with OSPF.

Gngogh

Just to clarify something... you have changed the network statement and the routers were able to perform adjacency ???

If so, its a bit wierd to me, because from what i know from OSPF the wildcard in the network statement as no influence in the mask address that is sent in hello packets.

I have done a little topology with 2 routers.

router0 - network 10.1.1.100 0.0.0.255 area 0

router1 - network 10.1.1.1 0.0.0.0 area 0

and the routers perform adjacency...

networker050184

You are correct Gngogh, the network command only matches on an interface IP. It has no influence what subnet mask is used.

This is one of my biggest pet peeves that people seem to misunderstand. I had to argue with a CCIE from Cisco TAC for about 20 minutes about this a few months ago. He was convinced that an all 0 mask would not work even though it is configured all over our (and many other) networks......

Dieg0M

networker is correct, in OSPF the mask of the network statement only influences the local interfaces in the up/up state that will form neighborship. It is the same for RIP and EIGRP. Only BGP will use the network mask in the network statement.

Gngogh

So the question remains, why the routers were not performing full adjacency????

RouteMyPacket

Gngogh wrote: »

So the question remains, why the routers were not performing full adjacency????

Buggy perhaps? I would have added the command I posted above to check but as stated above it absolutely should not matter and his original statements should allow the adjacency to form between BB1 and R1. PT has issues so I wouldn't be shocked if this is one of them, HSRP for example has a major bug in PT.

lsud00d

Dieg0M wrote: »

networker is correct, in OSPF the mask of the network statement only influences the local interfaces in the up/up state that will form neighborship. It is the same for RIP and EIGRP. Only BGP will use the network mask in the network statement.

*makes note*

JeanM

Good tips here!

kelsnjoku

when i entered the debug command, nothing happened (when routers couldn't form neighbors). I am yet to understand what that command really achieves though.

@all, surprisingly, BB1 and R1 have formed OSPF neighbors now and everything is working fine. I didn't change anything, I only restarted PT. I suspect the inability of the routers to form neighbors was an issue with PT just as RouteMyPacket hinted. I am now considering GNS3 for my practice even though I kind of find it daunting using GNS3.

thanks everyone for your input

MAC_Addy

GNS3 is brilliant, in my opinion. Though, it does take a little setting up. Mostly all issues are reported on their forums, so if you run into anything a quick google search will have you pointed in the right direction. Once you have it said and done it's amazing.