On 08/22/2012 06:09 PM, Hans van Kranenburg wrote:
So, it happened again yesterday. Exactly at the moment when one of my
collegues started a newly set up domU on one of our servers, a virtual
network interface of another (!) unrelated domU on the same dom0 began
failing. The affected system is one of a set of VRRP routers, which is
now taken out of order, and hangs around in a broken state.
[...]
One of the three network interfaces inside the domU shows exactly the
same behaviour I described before. There's no traffic possible from the
outside/dom0 to the inside of the domU, except when there's traffic from
the inside to the outside, suddenly old pings get ponged:
Yesterday we tried to do some more debugging.
The dom0 (say, dom0 A) where the domU with broken virtual network
interface (say, domU X) runs has 19 domUs running on it.
Test 1: live migrate domU X to dom0 B
--->X :)
A B
Result 1: network interface domU X on dom0 B OK
Test 2: live migrate domU X back to dom0 A
X<--- :(
A B
Result 2: network interface domU X on dom0 A broken
Test 3: xm shutdown domU X and xm create it again on dom0 A
X :(
A B
Result 3: network interface domU X on dom0 A broken
Conclusion: It seems there's some 'state' left on dom0 A so that when
domU X is placed back on dom0 A, it gets broken again.
But, is it only related to domU X?
Test 4: shutdown domU X and migrate another domU to dom0 A in its place
Y<--- :(
A B
Result 4: now network interface domU Y on dom0 A broken
Test 5: migrate domU X also back to dom0 A
X<--- :)
Y :(
A B
Result 5: network interface domU X on dom0 A OK
Test 6: extended version of test 4/5: remove domU X(OK), Y(broken) and
one extra domU Z(OK) from dom0 A. Now only 17 domUs run on dom0 A. Now,
move/start them back in another order: the 18th domU, X is OK, the 19th,
Z, shows up with broken networking.
It seems there's something like a 'place', (i.e. the 19th domU) on dom0
that's broken, and whatever domU we move in it shows broken networking.
I know everytime we start or migrate a domU to a dom0 vif devices etc.
are newly created instead of re-used, but its still always the 19th domU
that runs on this dom0 that invariably ends up with networking issues.
¯\(°_o)/¯
--
Hans van Kranenburg - System / Network Engineer
+31 (0)10 2760434 | hans.van.kranenb...@mendix.com | www.mendix.com
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