Linux networking crash: best steps to find out the cause?

Solution 1:

check

dmesg | less for anything related to your nic alias (i.e. eht0) less /var/log/messages aswell

Whilst rare it could of been an ip address conflict, if this should occur again try

arping -U <gateway ip> -I <nic alias> Check this however as it's been a long time since I have used arping and this may be incorrect.

If successful you should regain connection without reloading the network service.

Solution 2:

How are you getting your IP address on this network (DHCP, or static)? If it happens again, make sure to run ifconfig to look at the state of the interface while it's in its non-functional state. Does it have an address? Are there errors? If you run ethtool, is there a link? (And is it negotiated to the right speed and duplex?)