7609 reporting "Double-hop"

[chieftan]

Hi,

We have a very strange issue occuring that I would like to run past you guys and see what you think.

Lets try and keep it simple.

2 routers - running iBGP - Bristol and London (all locations and addresses changed, but scenario the same).

2 routers Meshed with 7609 chassis.

When performing a traceroute from Bristol to London we get a "Double-hop" at the 7609. Now, this is apparently a known issue with ICMP on 1 7609 chassis. Cool, no problem there and I will accept that. Last week the primary router failed and we switched to secondary. This was then fixed over the weekend and the Primary back online. Now when we complete a traceroute to the same device from Bristol to London we get the following traceroute result (IP addresses changed for security):-


1 2 ms 3 ms 2 ms 10.16.66.2
2 7 ms 2 ms 21 ms 10.16.60.89
3 11 ms 10 ms 10 ms 45.188.232.74
4 17 ms 18 ms 16 ms 10.16.70.20
5 16 ms 16 ms 19 ms 10.16.70.20
6 17 ms 16 ms 27 ms 10.16.90.212
7 18 ms 17 ms 17 ms 10.16.90.132
8 18 ms 18 ms 17 ms 10.16.70.20

Note the bold lines. It appears that the packet is bypassing all firewalls and edge routers, entering the site then exiting and re-entering again. Has anyone seen anything unusual like this before?

Thanks

 

[chieftan]

Apologies, forgot to add this:-

tracert 10.16.70.20