[CentOS] Problem with CentOS 5.1/xen/RTL8110

[Nicolas Sahlqvist]

On Jan 8, 2008 2:04 PM, Chris Gow <chris.gow at gmail.com> wrote:

> Hello:
>
> I'm having issues with my CentOS 5.1/Xen installation. If I run the
> xen-bridge, I seem to get flaky ethernet. By flaky I mean everything seems
> fine from the host machine, but if I attempt to contact the host machine
> from
> another remote machine (eg. my laptop which is on the same subnet as the
> xen
> machine, separated by 10 ft of cable and a router) I either get extremely
> high ping times or Destination Host Unreachable. Ditto with ssh. I've
> disabled the firewall and it does not make a difference. If I stop the
> xen-bridge (/etc/xen/scripts/network-bridge stop) then I get what I would
> consider normal network access to the xen machine.
>
> Hardware: Gigabyte GA-G33M-S2H MB (Realtek R8110SC onboard nic)
> OS: CentOS 5.1 64bit Xen
>
> I installed CentOS last night with the Xen kernel, the stock kernel did
> not
> support my nic which I was aware of. So I downloaded the r1000 source rpm
> from the centos wiki, built and installed it. Once I did that the card was
> detected (an ifconfig would actually display eth0), but it would never get
> an
> IP address (the xen machine is configured for dhcp at the moment). Today,
> I
> installed the non-xen kernel, applied the non-xen r1000 kernel module and
> the
> onboard nic was found and working.
>
> I then grabbed the updates from centos, saw that there were some kernel
> updates, applied the r1000 kernel modules again, restarted and (the
> non-xen
> kernel) eth0 was still happy. Good. Restarted again, but booted into the
> xen
> kernel, eth0 was still happy. eth0 would get an IP address, and was able
> to
> see the outside world. However, the outside world (eg. my laptop) could
> not
> see the xen machine or it could inconsistently. That is, ping times would
> be
> extremely high (on the order of 2+ seconds) or I would get Destination
> Host
> Unreachable errors. Trying to connect via ssh would also be sporadic.
>
> Thinking it might be firewall related, I disabled the firewall. There was
> no
> change in behaviour. I then disabled the xen-bridge and was able to ping
> with
> reasonable numbers (<200ms) and connect via ssh. Just to note though,
> after I
> stopped the bridge I immediately tried to connect via ssh/ping and did not
> get through, so I ran service iptables stop (again) and then was able to
> get
> correct network access. I'm not sure if stopping iptables again did
> anything
> (I doubt) or I did not leave enough time from stopping the bridge to
> letting
> everything get reconfigured.
>
> I'm not sure what the problem is or how exactly to troubleshoot it. The
> NIC is
> slightly different than the one specified in the CentOS wiki (the wiki
> mentions RTL8110 and RTL8169SC and mine is a RTL8110SC) but I'm not
> familiar
> enough with the devices to know how much of a big deal that is, if any.
> Also,
> just to be clear, the problem is other physical machines have a difficult
> time accessing the xen host pc when the xen-bridge is running. I have not
> gotten as far as creating a VM yet.
>
> Any assistance would be great.
>
> thanks
>
> -- chris
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>


Chris,

I got the impression that the network setup is as this example:

Your laptop (192.168.1.x/255.255.255.0)

Router (192.168.1.1/255.255.255.0)

Xen (192.168.1.x/255.255.255.0)

Well, you can't route from one physical network to another over a router
where source and destination has a ip in the same netmask area. Perhaps you
only use the router as a network switch since cheaper models have a built in
switch... In this case it's a switch rather then a router, some lousy home
scale routers may rally screw up things since they don't have switches,
rather a couple of network interfaces separated with bridging and firewall
rules in a embedded Linux or BSD environment..


- Nicolas
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