EIGRP neibouor command

DevilWAH

supose I have a router with three interfaces

192.168.1.254/24 s0/0
192.168.2.254/24 s0/1
192.168.3.254/24 s1/1

with a second router attached to the 192.168.3.0/24 interface/network

under eigrp router process i enter the following commands

#network 192.168.1.0 0.0.0.255
#network 192.168.2.0 0.0.0.255
#neibour 192.168.3.250 int s1/1 (or the correct form of that command )

and of course configure the other router correctly as well to responde. Will a relation ship form, or do i need to also enable the 192.168.3.0/24 network to be advertised?

billscott92787

This is where debug's definitely come in handy to watch and learn what is going on.

R1:

*Mar 1 00:04:32.679: %SYS-5-CONFIG_I: Configured from console by console
*Mar 1 00:04:33.395: IP: s=192.168.3.254 (local), d=192.168.3.253 (Serial0/0),
len 60, sending, proto=88
*Mar 1 00:04:33.807: IP: s=192.168.2.254 (local), d=224.0.0.10 (Loopback1), len
60, sending broad/multicast, proto=88
*Mar 1 00:04:33.815: IP: s=192.168.1.254 (local), d=224.0.0.10 (Loopback0), len
60, sending broad/multicast, proto=88
*Mar 1 00:04:33.827: IP: s=192.168.2.254 (Loopback1), d=224.0.0.10, len 60, rcv
d 2, proto=88
*Mar 1 00:04:33.831: IP: s=192.168.1.254 (Loopback0), d=224.0.0.10, len 60, rcv
d 2, proto=88
R1#
*Mar 1 00:04:37.735: IP: s=192.168.3.254 (local), d=192.168.3.253 (Serial0/0),
len 60, sending, proto=88
*Mar 1 00:04:38.091: IP: s=192.168.1.254 (local), d=224.0.0.10 (Loopback0), len
60, sending broad/multicast, proto=88
*Mar 1 00:04:38.099: IP: s=192.168.1.254 (Loopback0), d=224.0.0.10, len 60, rcv
d 2, proto=88
*Mar 1 00:04:38.219: IP: s=192.168.2.254 (local), d=224.0.0.10 (Loopback1), len
60, sending broad/multicast, proto=88
*Mar 1 00:04:38.219: IP: s=192.168.2.254 (Loopback1), d=224.0.0.10, len 60, rcv
d 2, proto=88


R2:
*Mar 1 00:04:41.759: IP: tableid=0, s=192.168.3.254 (Serial0/0), d=192.168.3.25
3 (Serial0/0), routed via RIB
*Mar 1 00:04:41.763: IP: s=192.168.3.254 (Serial0/0), d=192.168.3.253 (Serial0/


As you can see R2 is never getting any information about the 192.168.1.x or 192.168.2.x network. Nor is it forming an actual EIGRP adjacency. Even on Cisco's website it tells you to be careful with this statement because it doesn't work as intended, "Since the command does not behave as intended, the neighbor command should be used carefully, understanding the impact of the command on the network." (Cisco). I would stick to just using the network command to form your adjacency. It is the most reliable way, the neighbor command is made to send unicast packets to the neighbor with routing information. R1 multicasts to 224.0.0.10 the information about 192.168.1.x and 192.168.2.x. But as you can see from my debugs, it doesn't get passed to R2 with the neighbor command. As soon as I replace this with the network command on both sides the adjacency comes up and the routing table on R2 is complete.

DevilWAH

So yep I was looking at it whn back at work today. It seems if the network command is not invoked then the router /switch will never seend updates of any kind on that inter face.

once you add a neighbour comamnd then the interface it is applied to becomes a passive inter face and will not form neighbours with any other routers unless they are explicility set with there own neighbour command.

Which is exactly what I want. The network command is to generic, I dont want to form relations will all switchs on the same segment. or I do but I want them to form in a set way. by using the neighbour command I can force the distribuion sitches to form neighbours with the COre switchs but not with each other (for traffic managment) while still keeing them all on the same single subnet.

Basicaly I am laying a point to point router setup over a flat layer 2 physical network. This is an step to a full layer 3 set up, but for various resons I need to run both layer 3 and layer 2 across site at the same time for a while.

billscott92787

DevilWAH wrote: »

So yep I was looking at it whn back at work today. It seems if the network command is not invoked then the router /switch will never seend updates of any kind on that inter face.

once you add a neighbour comamnd then the interface it is applied to becomes a passive inter face and will not form neighbours with any other routers unless they are explicility set with there own neighbour command.

Which is exactly what I want. The network command is to generic, I dont want to form relations will all switchs on the same segment. or I do but I want them to form in a set way. by using the neighbour command I can force the distribuion sitches to form neighbours with the COre switchs but not with each other (for traffic managment) while still keeing them all on the same single subnet.

Basicaly I am laying a point to point router setup over a flat layer 2 physical network. This is an step to a full layer 3 set up, but for various resons I need to run both layer 3 and layer 2 across site at the same time for a while.

I think I understand what you are saying now. When your implying the neighbor command it disables sending updates on those interfaces so an adjacency "won't" form. You can then define the network command between your switches that you want to form an adjacency, so that you only have a neighbor relationship between those areas instead of all switches in the entire network/subnet.