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
On Jan 8, 2008 2:04 PM, Chris Gow chris.gow@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 _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
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
Chris,
I got the impression that the network setup is as this example:
Your laptop (192.168.1.x/255.255.255.0)
Router (192.168.1.1/255.255.255.0http://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
Nicolas, I am following this thread with interest as a system I was about to setup is using the same driver and in the same networking scenario! If in a small segment with only one subnet and the default gateway on that subnet as you describe above, the Xen machine even in bridged mode won't have connectivity if Dom0 has an ip on the same subnet? Giving the Xen machine an IP on a different subnet would make it tricky to connect from another machine in this setup?
Thanks! jlc
I am following this thread with interest as a system I was about to setup is using the same driver and in the same networking scenario!
Then, you'd want to subscribed to the centos-virt mailing list:
http://lists.centos.org/mailman/listinfo/centos-virt
I believe this subject has been moved over there.
Akemi
On Jan 8, 2008 5:22 PM, Joseph L. Casale jcasale@activenetwerx.com wrote:
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
Nicolas,
I am following this thread with interest as a system I was about to setup is using the same driver and in the same networking scenario! If in a small segment with only one subnet and the default gateway on that subnet as you describe above, the Xen machine even in bridged mode won't have connectivity if Dom0 has an ip on the same subnet? Giving the Xen machine an IP on a different subnet would make it tricky to connect from another machine in this setup?
Thanks! jlc
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Joseph,
The only time I hit into this kind of problem is when using VPN sitting on the same subnet locally as on the other end of the tunnel so the VPN client is unable to route it over to the same subnet on the other side, this is quite expected behavior why one have to put another route between the client pc or change the ip range of the local network and then set up a VPN tunnel.. But on a local network where you have a Xen instance on 192.168.1.110, the Dom0 host on 192.168.1.100 (bridiging in between as default with Xen) with a gateway of 192.168.1.1 I don't see the problem, the clients on the network can access both last time I tested. I would be really surprised if this would have passed broken through RH and CentOS testing phases.
Chris Gow wrote:
Hello:
I'm having issues with my CentOS 5.1/Xen installation. If I run the
just want to remind people that there is a centos-virt list which was setup to address just these sort of issues.
-
Akemi Yagi -
Chris Gow -
Joseph L. Casale -
Karanbir Singh -
Nicolas Sahlqvist