Would that be an MTU of 296 ?
> If no one is experiencing this on other network types, then maybe
> the error has to do with serial lines only?
ping -s [alan@roadrunner anarchy]$ ping -s 4000 distraction
PING distraction (163.164.61.245): 4000 data bytes
4008 bytes from 163.164.61.245: icmp_seq=0 ttl=64 time=12.1 ms
4008 bytes from 163.164.61.245: icmp_seq=1 ttl=64 time=10.9 ms
4008 bytes from 163.164.61.245: icmp_seq=2 ttl=64 time=11.0 ms