In another thread I was asking about losing network connectivity of an
AIX box outside its
subnet, while there are no problems with another box (same AIX) on
another subnet.

I see one "significant" difference between the outputs of "netstat -

xxx.yyy.208/21 xxx.yyy.208.248 U 8 6538 en0
- - <===== Box w/ problem

xxx.yyy.204/24 xxx.yyy.204.101 U 1 0 en0
- - <===== Box w/o problem

What would be the reason for the seemingly big traffic going thru one
host and none thru the
other? Could this ever increasing amount of transfer be responsible
for losing connection?

In the example above connectivity to-and-from xxx.yyy.208.248 was
restored by a reboot,
and pmtu discovery has been switched off, while pmtu discovery stays
on on the other box.

Also, these routes are system-generated, not manually added.