Re: Blocked port 25?

[Michael.Dillon () radianz com]

> I've found a similar problem... From www.traceroute.org i can trace to a 

> server from some countries and not others... and even some states and 
> not others... 

This is something that was seen when DCEF over so-called parallel
paths was commonly used. It was a result of a hashing algorithm
that chose certain source IP addresses to take one path and
other IP addresses to take another. In that case, the effect
showed up when one person at a site had a problem and another
person did not. Obviously, DCEF alone will not cause problems
because it just sends traffic down different paths and there
was something else causing the two paths to behave differently.

Nowadays some people are using MPLS to load balance traffic
between two LSPs. But if the two routers at the ends of
the alternate LSPs do not have the same view of the network
then you can get this sort of effect.

Presumably you have verified that traffic sourced in one
provider's network behaves differently depending on what
part of the network you source it from? If I were you, I
would isolate the problem to one provider's network and then
work with their NOC to do further troubleshooting.

--Michael Dillon