North American Network Operators Group|
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Re: Blocked port 25?
> 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