EIGRP TTL trouble

[#1]

I have a cisco router 3945 that sends EIGRP packets with TTL = 1 and a cisco 3845 that sends EIGRP packets with TTL = 2, in the middle of the routers I have a web filter in transparent mode that decrements the TTL, so I'm having trouble doing EIGRP neighborhood between my routers because packets from 3945 to 3845 are discarded because the TTL is 0.
Is there any way to increase the EIGRP TTL on the Cisco 3945 router

thank you very much

[Julio E. Moisa]

Hi Mayra, 

I understand EIGRP use TTL 2 by default for multicast into NBMA networks. How is your topology?

Could you please share the config on both routers?

[cofee]

Neighbor command under the eigrp process will give you a ttl of 2. You can use that as a work around on 3945.

[cofee]

Would like to add that neighbor command need to be added on both routers as eigrp router stops listening on multicast address 224.0.0.10 once neighbor command is added.

This should resolve your issue as the device in the middle is decrementing the ttl by 1.

Router eigrp 1

neighbor x.x.x.x outgoing interface

You will need this on both routers. I hope this helps you.

[Julio E. Moisa]

Hi

Take in consideration that using neighbor command it will create unicast relationship, now if there is other router or others will be included in a future you could need to disable the split-horizon in order to avoid problems between the routers.

:-)

[cofee]

Julio - You are right that it may require disabling split horizon if more eigrp speaking routers are added out the same interface. Shouldn't have any negative impact as eigrp uses feasibility condition to prevent routing loops.

In my understanding other options would be to create a tunnel between 2 routers to bypass the filtering devices, but this defeats the purpose of going through that device in the first place. BGP peering can be created between these routers and then redistribute eigrp over BGP, this design over complicates the whole topology. May be you can think of something else in order to overcome this problem.

[Julio E. Moisa]

Hi Cofee@0400

I agree with you, the neighbor command could work and set the TTL to 2. I remember EIGRP usually set TTL to 2. 

Hi Mayra could you please try the configuration mentioned by Cofee, it should be: 

Edger router:

neighbor 172.21.48.1 G0/0

Internal router:

neighbor 172.21.48.2 G0/0

Assuming these IP addresses are able to communicate, It should be an option. 

I like the idea to use iBGP instead Eigrp and redistribute into EIGRP, there are other ways like configure a Proxy on the hosts. 

[#8]

I have other routers 3925 and 3945 and in both I get EIGRP packets and I see that their TTL value = 1. In the Cisco 3825 and 2811 Routers I see that EIGRP packets have TTL = 2