Comcast business IPv6 vs rbldnsd & PSBL

Mikael Abrahamsson swmike at
Tue Nov 29 19:43:55 UTC 2016

On Tue, 29 Nov 2016, Rik van Riel wrote:

> Not a symptom I ever expected to see...

It's pretty obvious that the CPEs being sold for this "business service" 
isn't meant for the kind of service you run.

They're probably doing connection tracking for ACK optimization, this 
should not be done for UDP but it's still being done. They probably have a 
connection limit of a few thousand connections (not uncommon for these 
kinds of devices) and it's not possible to turn off what you need to turn 
off to make them work correctly.

Do you have any other options in your area for other ISPs that can offer a 
better service for you?

Otherwise you might hack around it by running an IPSEC/UDP tunnel to 
somewhere else where there isn't this kind of connection limit.

Mikael Abrahamsson    email: swmike at

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