I have problem that driving me nuts for 3 days now.
I've tried run some .NET soft on one of our server's and after update (from official repo + badgerports) the network stop working. I intend to update only mono stuff, but I made apt-get update + apt-get upgrade. A lot of packages was installed (it was fresh ubuntu installation)
I've done it using ssh, I do not lost the connection but the next day I was unable to log in. The server is invisible from the external network.
The interesting thing is, that I'm still able to log in from neighbor server (probably connected to the same switch, I know it communicate using MAC address only).
The ip address configuration of the problematic host is static. ifconfig shows that interface receive some packets (it must cause the ssh is working). The problem is that it cannot connect to default gw. The ping to it does not reply, but it correctly resolve hw address of the gateway (checked using 'arp' command). Swapping switch sockets with the working host does not help, switching ip's neither, so it's definitely configuration problem
When I run iftop I see that it receives broadcast packets, but no host reply to it's request.
'iptables -L' returns empty table (the same on the working host) 'route' shows only broadcast network and default gateway
content of /etc/network/interface:
auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet static address X.Y.121.117 netmask 255.255.255.0 network X.Y.121.0 broadcast X.Y.121.255 gateway X.Y.121.250 dns-nameservers X.Y.96.9