[Fedora-xen] No network on FC6 host system

[Kenneth Jensen]

I just upgraded a Xen host system from FC5 to FC6, and with that I
lost networking...

When I boot the system without starting the xend service, networking is fine.
I have removed all iptables rules, so there is just "-j ACCEPT" for
INPUT, OUTPUT and FORWARD chains. Everything is A-OK.

When I start the xend service, it brings up the vif0.1 and the peth1
and connects them with xenbr1. Then I lose all connectivity. Atfer
that, I can ifup and ifdown all day, play with brctl and whatnot -
nothing seems to help but rebooting the system.

I even tried removing all xen software, remove the config directory,
reboot the system and then  installing the whole thing again - to get
the default configs. And before that, my configs were pretty
straight-forward - nothing fancy.

I keep thinking I overlooked something obvious... Any hints?

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Cheers,
Kenneth