[CentOS] network connectivity lost after reboot/upgrade

Mon Mar 4 21:54:04 UTC 2013
James Hogarth <james.hogarth at gmail.com>

> thanks for the tip, but, unfortunately, this cannot be the case here.
> Networking of the host is also affected, even when Xen is shut off.
> I have no smart switches in this office and I ruled out switches by using
> a direct connection to the laptop.

So it's something unrelated to xen...

Is the host using a static address or dhcp?

If you tcpdump do you see all the packets you'd expect for layer 2
connectivity (ie ARP requests and responses?)

Does ss or ifconfig show any transmit or receive errors? Do packet counts
go up?

Given that ethtool states the link is up I'd statically configure an
address and try to ping the gateway whilst running tcpdump ... Then take
the packet dump (-w filename to save it) and take a look in wire shark ...
You should see 'who has gateway IP' as an ARP request and the response from
the gateway... Along with the ICMP echo-request and echo-reply packets...

>From there you can start diagnosis properly...