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I have been setting up a xen server with 10.04 LTS server installed.

Every so often, the network seems to hang.

For example

64 bytes from 192.168.1.109: icmp_req=1317 ttl=64 time=0.381 ms
64 bytes from 192.168.1.109: icmp_req=1318 ttl=64 time=0.397 ms
64 bytes from 192.168.1.109: icmp_req=1319 ttl=64 time=0.402 ms
64 bytes from 192.168.1.109: icmp_req=1320 ttl=64 time=0.391 ms
64 bytes from 192.168.1.109: icmp_req=1321 ttl=64 time=0.403 ms
64 bytes from 192.168.1.109: icmp_req=1322 ttl=64 time=0.380 ms
64 bytes from 192.168.1.109: icmp_req=1323 ttl=64 time=0.394 ms
64 bytes from 192.168.1.109: icmp_req=1324 ttl=64 time=0.370 ms
64 bytes from 192.168.1.109: icmp_req=1325 ttl=64 time=0.385 ms
64 bytes from 192.168.1.109: icmp_req=1326 ttl=64 time=0.400 ms
64 bytes from 192.168.1.109: icmp_req=1327 ttl=64 time=0.373 ms
64 bytes from 192.168.1.109: icmp_req=1328 ttl=64 time=0.390 ms
dsf


ssd


64 bytes from 192.168.1.109: icmp_req=1354 ttl=64 time=0.403 ms
64 bytes from 192.168.1.109: icmp_req=1355 ttl=64 time=0.415 ms
64 bytes from 192.168.1.109: icmp_req=1356 ttl=64 time=0.426 ms
64 bytes from 192.168.1.109: icmp_req=1357 ttl=64 time=0.405 ms
64 bytes from 192.168.1.109: icmp_req=1358 ttl=64 time=0.420 ms

First off, this output is weird. just before I tapped on the keyboard producing dsf to where the network came back below tapping ssd I would have expected the time to be large. i.e. in the order of about 15 seconds as that is how long it took to come back.

As it so happens, this ping output was from another machine to the xen server. I have a very similar output from the xen machine to my other machine.

While this was going on, I had a ping to google.com running and this pausing did not happen.

What could be causing this? I have no virtual machines running yet.

I would like to point out, that I have had this exact same issue occur on another high end xen testing computer (different hardware). I'd like to be able to say it's a simple configuration problem, or a known issue with Ubuntu 10.04 LTS.

By the way, the server is using DHCP. I'll try first setting it to a static address and see what effect that has if any.

* EDIT * There seems to be some problems in Ubuntu Server 10.04 with the DHCP client. What I've found is firstly that the dhcpd.leases file could not be written to because of a path problem. So creating /etc/dhcp fixed that.

But the problem still existed.

Changing to a static IP and the problem is completely gone. However, I do want to use DHCP to provision some dynamic xen servers so I do need to solve this. I might try updating the dhcp package.

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I'm not seeing this issue with the latest ubuntu server 10.04 LTS or one of it's recent updates. Perhaps it's been fixed. –  Matt H Mar 23 '12 at 5:04

1 Answer 1

Hmm, this might actually be a bug. If you perform a dhclient directly on the guest do you observe any checksum errors?

http://old-list-archives.xen.org/archives/html/xen-users/2011-06/msg00561.html

If so, try disabling the PV network driver and retest. The user in the post above with the same scenario can avoid the problem while in pure HVM mode. If you can confirm this please file a bug.

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