Help me make sense of these traceroutes please

Jeroen Massar jeroen at massar.ch
Tue Dec 24 23:55:46 UTC 2013


On 2013-12-25 00:16, Sam Moats wrote:
> Hello Nanog community,
> I would like to enlist your help with understanding this latency I'm
> seeing.

You are likely seeing the effects of asymmetric routing.

[..]
> Tracing route to xxx.yyy.ie [193.1.x.x]

www.heanet.ie by chance? :)

Though you could use for instance:
http://planchet.heanet.ie/toolkit/gui/reverse_traceroute.cgi

to do a reverse traceroute, do make sure you force your connectivity to
IPv4 as that host will do IPv6 too. (locally nullrouting the destination
/128 is the trick I use for 'disabling' IPv6 temporarily).

Otherwise the HEANET folks are extremely helpful and clued in, you can
always ask them for help with issues. It is the end-of-year though and
those Irish folks have lots of really good whiskey, Guinness thus you
might have to be patient till the new year.

Alternatively, you could use a tool like 'tracepath' or 'mtr' as those
reports multiple answers to a response and also check for the TTL on the
return packets.

Greets,
 Jeroen




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