Xen: can't get Dom0 and the DomUs to ping eachother

Oh my, so old... But since I got here while trying to find a solution, here's one. I think your problem is in "ip=192.168.1.2" at your vif line, but if I'm wrong, the answer is useless. And even if I'm right, it's useless for people with even slightly different config. Therefore, long version:

DomU network config (everything else doesn't matter): vif=['bridge=xenbr0']

Bridge is configured over the dummy interface, made up like this (these are commands executed as root):

# modprobe dummy
# ifconfig dummy0 up
# brctl addbr xenbr0
# brctl addif xenbr0 dummy0

Here's how it looks after you start your VM (you can see VM's vif16.0 attached to your bridge):

# brctl show
bridge name     bridge id               STP enabled     interfaces
xenbr0          8000.1a088b6b402f       no              dummy0
                                                        vif16.0

I use DHCP, but you could assign IP's manually. To xenbr0 for Dom0 and eth0 under DomU for DomU. Do not assign any IPs to your bridge members! This is important.

ifconfig for Dom0 looks like this (removed stats to make it less bulky):

dummy0    Link encap:Ethernet  HWaddr 1a:08:8b:6b:40:2f
          inet6 addr: fe80::1808:8bff:fe6b:402f/64 Scope:Link
          UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1

vif16.0   Link encap:Ethernet  HWaddr fe:ff:ff:ff:ff:ff
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

xenbr0    Link encap:Ethernet  HWaddr 1a:08:8b:6b:40:2f
          inet addr:192.168.2.1  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::1808:8bff:fe6b:402f/64 Scope:Link

And from DomU looks like this:

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
    inet 192.168.2.21  netmask 255.255.255.0  broadcast 192.168.2.255
    inet6 fe80::216:3eff:fe25:e843  prefixlen 64  scopeid 0x20<link>

Pinging Dom0:

PING 192.168.2.1 (192.168.2.1) 56(84) bytes of data.
64 bytes from 192.168.2.1: icmp_seq=1 ttl=64 time=0.238 ms
64 bytes from 192.168.2.1: icmp_seq=2 ttl=64 time=0.279 ms

And for internet access (my configuration is essentially NAT, yours should have internet access natively) enabling NAT may be required like this:

iptables -t nat -A POSTROUTING -s 192.168.2.0/24 ! -d 192.168.2.0/24 -j MASQUERADE

For troubleshooting use tcpdump -v -i xenbr0. It helps a lot as successful Ping requires your packet to get out and return, therefore gives you no clue about when it is lost - while getting out or coming back.

Xen: can't get Dom0 and the DomUs to ping eachother

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