TTL 1 of EIGRP can be possible on Catalyst3650/3850?

[mhiyoshi]

Dear all,

Normally IP Header's TTL value of IPv4 EIGRP is "2" which can be supported under Frame-Relay or DMVPN Hub & Spoke topology etc.

I have checked it with IOS Router, it was actually "2". However according to the above product, it might be TTL "1" which are  Catalyst IOS-XE. It is little bit uncertain information so I appreciate if somebody let me know any IP header of EIGRP capture data on these products.

Besides if I want to increase this TTL value, my idea is just to configure Tunnel Interface which add TTL "255" value

however any other possible configuration?

Best Regareds,

Masanobu Hiyoshi

[pieterh]

why would you increase the value?
the purpose of this TTL is to be able to reach the EIGRP neighbor, not a 255th neighbor from the source?
NB! the neighbor at the end of the tunnel is a single hop!

[mhiyoshi]

Hi pieterh,

Yes the reason is because there is Firewall between EIGRP routers, for example the topology is like the following.

Router1 ------ FW (with decrease-TTL) ------ Router2

So if the TTL value is 1 then FW's policy decrease it from 1 to 0, then the neighborship can not be established.

Currently the FW's policy can not be changed due to customer policy.

However I would just like to know there is any specification of the difference such as RFC/CCO etc.

Best Regards,

Masanobu Hiyoshi