[lug] weird networking on a multi-homed host

[Hugh Brown]

I have a host acting as a firewall with two NIC's in it.  I was trying to
do a net install on it (with the external NIC disconnected) and I couldn't
get anything to go.  So I did some testing.  eth0 is the external interface
and eth1 is the internal interface.  server is the multi-homed host and
client is a machine on the internal lan.

when I disconnect the cable to server:eth0 and try and ping client from
server, I get next to nothing showing up on server.  When I sniff packets
on client though, I see all of the ping requests come through just fine.
If I ping server from client I see all of the requests come back fine, but
the sniffer on server shows nothing coming through.

So

ping server->client   mostly fails (I get about 5 responses, the first one
shows up after a while, but shows a 1ms response time, the next response
showed 80000ms, then 160000ms, then 320000, then 640000 ...)

ping client->server works fine

I'm at a loss.

Hugh