Half vent, half advice post.
So I just spent the morning (~ 4 hrs) trying to debug this one... Debian server, inherited. Has always run with single NIC. A couple months ago I installed a second NIC for another network. A couple days ago I installed a new client, and wanted to ssh from it to the server. Can't. Won't.
... and iptables is not the problem... ... and there is no tcpwrappers installed...
tcpdump reports SYN packages from the troublesome client go unaswered (meaning the server is not even responding to the initial connection attempts, as if it wasn't there... but only for that troublesome client)...
I probably should've done this sooner, but given there were connections from some clients, it couldn't be network, right? Except it was.
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
X.X.X.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
0.0.0.0 192.168.0.254 0.0.0.0 UG 0 0 0 eth1
0.0.0.0 X.X.X.254 0.0.0.0 UG 0 0 0 eth0
That eth1? Configured to "manual" in interfaces.
Sigh.
[link][12 comments]