Total Networking Failure after upgrade to 12.04LTS

Graham Todd gct7photography at gmail.com
Sun Jul 28 15:53:40 UTC 2013


On Sat, 27 Jul 2013 10:03:19 -0400
Hal Burgiss <hal at burgiss.net> wrote:

> After a server upgrade from 10.04LTS to 12.04LTS, which otherwise
> seemed very normal, networking is non-functional. Nothing works
> (ping, dns, ssh, etc). Cannot ping any address, even on the LAN, and
> the system is not pingable from other systems on the LAN.
> 
> The system in question is a 3 yr old Dell PowerEdge R510 server with
> duel NIC's, both are Broadcom NetXtreme. This system has no history
> of problems, and is used as a file server and internal DNS server for
> an office LAN. The original configuration bonded the 2 NIC's. The
> system is typically managed remotely via ssh (and thus I have no good
> way of copy/pasting screen output). There are no gui tools installed
> -- its a server. There is no unusual routing or networking
> configuration (other than the bonding). No VPN. Just a very typical
> single default gateway type set up.
> 
> After the upgrade to 12.04, there just is no functional networking of
> any kind.
> 
> What's been tried:
> 
> - pinging localhost and the local network ip address on the NIC both
> work normally. pinging anything else, including the default gateway
> by ip address, fails with "network unreachable".
> - take firewall up / down
> - remove bonding (pretty sure this was problematic after the upgrade)
> + reboot
> - tried NIC's one at a time individually -- identical behavior
> - manually reconfigured NIC's with ifconfig and route commands to
> make sure there wasn't a config file change that was problematic.
> - manually compared the output of ifconfig and route to another
> similar working
> system (10.04LTS) in the same rack (no difference other than the ip
> address)
> - tried setting NIC's to dhcp (times out)
> - turning off apparmor (desperation)
> - disabled ipv6 with sysctl (more deperation)
> 
> Other factoids:
> 
> - Boot sequence looks normal, NIC's are recognized and are shown as
> "ready". No errors reported.
> - No errors in kern.log or syslog, ever.
> - No errors shown by ifconfig.
> - Very strangely ifconfig will show both TX and RX steadily
> incrementing. I can ping and watch both values change, but pings
> timeout.
> - When the firewall is up, it shows normally looking volume of
> packets in both the INPUT and OUTPUT chains. iptables apparently sees
> incoming traffic. Symptoms are the same with firewall up or down.
> - tcpdump will show arp traffic only, and nothing else. But
> interestingly it shows a lot of packets "dropped by kernel".
> 
> 'tcpdump -vv -X' output summary will look something like:
> 
> 15 packets captured
> 369 packets received by filter
> 350 packets dropped by kernel
> 
> I haven't found anything except arp traffic by tcpdump. So does
> anyone know what causes "packets dropped by kernel" other than maybe
> iptables? Or is this an artifact of something else being wrong, like
> dns not working? Or other ideas of what to try?
> 
> 
> 

You seem to have tried everything I would.  I guess now's the time to
try another distro until someone more knowledgeable that I can fin out
what's going wrong.

I'd recommend going for Nota Linux if you still want to persist with a
flavour of Ubuntu.  You can get it at:

http://www.notalinux.com/

and I've been using 12.04 very successfully with it, or if you don't
want to try a flavour of Ubuntu, try gNewSense, which you can find at:

http://www.gnewsense.org/Main/Download

I've had both of them on my desktop and laptop computers, and both
worked 'out of the box' when I tried to connect via wireless and wired
routers respectively.

If you do try another distro, don't forget to backup, something I did
not do (again!).

Graham
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