Hello,
I am installing xen-3.0.31 on debian-etch-r7 version (apt-get install
xen-linux-system-2.6.18-6-xen-686 screen ssh debootstrap python
python-twisted iproute bridge-utils libcurl3-dev libssl0.9.7). My eth0
is configured to get IP via dhcp (interfaces file attached). I am able
to boot into dom0, but starting xenbr0 causes loss of IP connectivity.

Here is what I do. Initially, my /etc/xen/xend-config.sxp looks like this
[...]
#(network-script network-bridge)
[...]
(network-script network-dummy)
[...]
(vif-script vif-bridge)
[...]
Now when I boot into dom0 - I can ping www.google.com. The output if
ifconfig is in the attached "before" file. Obviously, brctl show does
not show any bridge.

Then I comment out the network-dummy line, uncomment the
network-bridge line and reboot. This time, I can see (from the boot
messages) that the bridge xenbr0 is being created. Then when I log
into dom0, I cannot ping google.com

brctl show and ifconfig outputs are in the attached "after" file.

Any help in solving this will be greatly appreciated.
Thanks.