🚀 go-pugleaf

A machine here has had a recurring problem that is about to drive us crazy.

A VAX-11/780 running ULTRIX has several network interfaces: a PRONET, a
3-Com Ethernet, a dmr-11 and a DEC DEUNA. All work fine except the DEUNA.
On a fairly regular basis, the machine becomes incapable of sending good IP
packets out through the DEUNA, although it continues to receive them just
fine.

I suspect that packets are still going out with good Ethernet CRCs, except
that their contents are garbled; the "bad IP header checksum" counts on
other machines start increasing whenever the VAX attempts to send packets to
them. Rebooting temporarily fixes the problem, for perhaps 12 hours or so.

This problem is particularly aggravating because it prevents alternate
routes through its other interfaces from being used. The fact that the
DEUNA's receiver continues to work means that the router continues to
believe that it can reach sites through that interface. Worse, it broadcasts
this bogus information to sites on its other interfaces.

Can anybody help? We're going to need toupees pretty soon.

Phil