3750 , EIGRP , Routed ports

[SZ1]

Hello all,

Scenario :

Our company is having ring of WAN links terminated on Cat 3750's...i.e. each of our 4 offices has 2 * 100 Mbps WAN links connected to the neighboring offices....

RING - A to B , B to C , C to D and D to A and we use EIGRP on WAN for resiliency.... ( C to D is not connected as of now because of which I am raising this query here )

All links use routed ports except the one between A to D....because between A to D we have service provider with their own L3 switches connecting to my 3750's. So as per the current config my 3750 at A & D have management VLAN configured and speaking to service provider L3 switches using EIGRP...so A has management subnet as 89.0.0.0 & D has management subnet as 90.0.0.0

Problem :

I am trying to install C to D link but it is not getting installed because when I enable the ''C to D'' WAN link the Switch D which has 90.0.0.0 as its management Vlan starts learning 90.0.0.0 via ''C to D'' WAN IP ( 91.0.0.0 ) via EIGRP....and morever I cant ping Switch D IP ( 90.0.0.8 ) from my own switch but I can ping & telnet to it ( via the newly learned long route ) .....

When I enable new WAN link...

SW02#sh ip route 90.0.0.8

Routing entry for 90.0.0.0/24

Known via "eigrp 9", distance 90, metric 44032, type internal

Redistributing via eigrp 9

Last update from 91.0.0.1 on GigabitEthernet2/0/23, 00:00:00 ago

Routing Descriptor Blocks:

* 91.0.0.1, from 91.0.0.1, 00:00:00 ago, via GigabitEthernet2/0/23

Route metric is 44032, traffic share count is 1

Total delay is 720 microseconds, minimum bandwidth is 100000 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 8

When I disable new WAN link...

SW02#sh ip route 90.0.0.8

Routing entry for 90.0.0.0/8

Known via "connected", distance 0, metric 0 (connected, via interface)

Redistributing via eigrp 9

Routing Descriptor Blocks:

* directly connected, via Vlan1

Route metric is 0, traffic share count is 1

All Cat 3750 : Version 12.2(25)SED1 , c3750-ipservicesk9-mz.122-25.SED1.bin

Solution :

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[kamlesh.sharma · Accepted solution]

where is this switch sw02

your both the show ip route output are showing different subnetmask for the network.try using show ip route and post it again.

Directly connectly routes will always be in routing table and it cann't be replaced by any routing protocol bos of AD is 0 for directly connected route.

[SZ1]

Q. where is this switch sw02

A. SW02 is at Location D

Q. your both the show ip route output are showing different subnetmask for the network.try using show ip route and post it again.

A. That is exactly what the problem is....I dont have any subnet as 90.0.0.0/24 still it learns it when I enable ''C to D'' link....and when I disable the ''C to D'' link it learns it rightly as 90.0.0.0/8 which is what my network is configured for....cant give you the out put with subnet mask now because I cant enable the new link during the network is LIVE....

Q. Directly connectly routes will always be in routing table and it cann't be replaced by any routing protocol bos of AD is 0 for directly connected route

A. I got your point but this is what is happening...Although my 90.0.0.0/8 is a directly connected subnet , once I enbale the new ''C to D'' WAN link EIGRP replaces it with 90.0.0.0/24 and route via the new WAN link IP....

[atif.awan]

I am pretty sure your 90.0.0.0/8 is not being removed from the routing table. What is actually happening is that for some reason you start getting a 90.0.0.0/24 and this gets installed in the routing table. Since this is a more specific route packets to 90.0.0.8 will always prefer this route. This is what I think is happening based on the information available so far.

I would like to see the output of the show ip route 90.0.0.0 from your switch C at least and also from other switches if possible (the output should be obtained when the link between C and D is not connected).

[SZ1]

hi atif....

good point....I will give you points if it solves my problem and I think it will....

I just saw that A which is connected to B via service provider L3 switch is learning B as 90.0.0.0/24 ( totally unexpected ) whereas B learns A as 89.0.0.0/8 ( as expected )......

I havent informed my senior colleagues about this post as of now but would tell them once the problem is solved....

Cheers

[SZ1]

my issues is not yes resolved....Im using this forum for first time ....I think if you give ''3'' to two responses the Forum considers it as good enough to resolve the issue.....First I gave 3 to Atif & 3 to Kamlesh and I dont know how it Forum put it in resolved....

Atif you were equally good....Thanks....

I will keep you posted once its is resolved anyway....

[atif.awan]

The forum should not consider it resolved unless you choose the 'resolved' option when you submit a vote. By the way do not worry too much about the forum ratings right now (even though you should definitely rate helpful posts).

I thought that it was Swithc A and Switch D that are connected via SP Layer-3 device and not Switch A and Switch B?

It could be an issue with the provider advertising the route with incorrect mask but I will let you troubleshoot it since it is faster as you have access to the devices :). If the problem is not resolved please let us know and we will ask you for additional information (show ip routes from switches, configuration snipets, etc.) to try to help you.

[SZ1]

it is between Switch A & D....I mentioned it as B wrongly in excitement to see how close I am to solve that problem....

Cheers