Comcast, DHCP and MTU

If you are a Comcast customer (particularly in Illinois) and your Voice-over-IP (or other large-UDP-packet-using) application does not work as it should, don’t worry, it’s their fault. :P

For some reason, they include

...
OPTION:  26 (  2) Interface MTU             576
...

in the replies from their DHCP …

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