Next hop issues inside AS577 to AS852?

Sat Jul 31 11:51:58 UTC 2004

Unfortunately, I am not a direct customer of AS577 otherwise I would open a 
ticket with them, but we have a lot of sites inside Bell Canada that need 
to reach us.

Starting suspiciously at maintenance window time, we were seeing sporadic 
reachability issues coming at us from Bell. I am pretty sure its to us, and 
not the other way around as exiting out, I always prefer my GT/360 link and 
depending on the source IP it always works.  The path back to me was via 
AS852 (telus) but I had to massively prepend to force it via someone else 
to get things working.

But here are 2 traceroutes from inside AS577 (Bell) back to me

Traceroute a)
194# traceroute -n 64.7.153.1
traceroute to 64.7.153.1 (64.7.153.1), 64 hops max, 44 byte packets
  1  209.226.183.241  266.863 ms  219.712 ms  199.588 ms
  2  206.172.130.250  219.408 ms  219.700 ms  209.619 ms
  3  206.47.229.8  239.433 ms  195.376 ms  193.984 ms
  4  64.230.241.125  229.460 ms  199.675 ms  209.669 ms
  5  64.230.242.150  209.415 ms  189.707 ms  199.627 ms
  6  154.11.3.25  239.440 ms  219.684 ms  208.091 ms
  7  154.11.6.17  241.001 ms  217.379 ms  231.976 ms
  8  64.7.143.44  229.456 ms  199.648 ms  189.635 ms
  9  64.7.143.45  224.784 ms  194.333 ms  189.678 ms
10  64.7.153.1  229.431 ms  209.654 ms  209.672 ms

traceroute b)
194# traceroute -n 64.7.153.1
traceroute to 64.7.153.56 (64.7.153.56), 64 hops max, 44 byte packets
  1  209.226.183.241  278.871 ms  221.986 ms  189.687 ms
  2  206.172.130.250  219.433 ms  229.680 ms  339.650 ms
  3  206.47.229.19  239.447 ms  189.621 ms  195.621 ms
  4  64.230.241.121  223.483 ms  209.663 ms  199.695 ms
  5  64.230.242.97  329.445 ms  209.667 ms  229.666 ms
  6  64.230.242.181  239.463 ms  196.798 ms  192.568 ms
  7  * * *
  8  * * *

Every 60 seconds or so the path back to me inside AS577 would change back 
and forth between a) and b).  I dont know what Hop 7 on b) is. It could be 
another peer to AS852 (Telus) or just another internal router at Bell 
(AS577).  Suffice to say, when taking path b) packets never get back to me.

To work around it, I had to prepend out my AS852 link so that Bell comes 
back at me via GT/360 or Cogent.

Anyone from Bell or Telus around to clarify where the problem is?  Sadly, 
this is a holiday long weekend here in Canada :(  The wheels fell off 
around 4:30 AM EST.

         ---Mike

--------------------------------------------------------------------
Mike Tancsa,                                      tel +1 519 651 3400
Sentex Communications,                            mike at sentex.net
Providing Internet since 1994                    www.sentex.net
Cambridge, Ontario Canada                         www.sentex.net/mike