[Xen-users] setting up private networking between dom0 and domU?

[Jack Snodgrass <mylinuxguy@xxxxxxxxx>]

I am trying to set up dom0 <->domU networking using a
virtual switch, a tap device on dom0 and a NIC on domU.

I have domU <-> domU connectvity throguth a virtual switch.
I also have domU <-> eth0 using a bridge. I'm using Xen 3.0
from Fedora FC5.

I used these commands to set up the tap0 and sw2 device:

  # creating switch 2
  brctl addbr sw2
  brctl stp sw2 off
  brctl setfd sw2 0
  ifconfig sw2 up

 # creating tun/tap device
 tunctl -t tap0

# adding tun/tap device to bridge
brctl addif sw2 tap0

# configuring tap0 device
ip address add 192.168.3.2/29 dev tap0
ifconfig tap0 up

ifconfig shows:
[root@xen xen]# ifconfig sw2
sw2       Link encap:Ethernet  HWaddr A6:44:26:ED:AC:5F
          inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:259 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:7252 (7.0 KiB)  TX bytes:468 (468.0 b)

[root@xen xen]# ifconfig tap0
tap0      Link encap:Ethernet  HWaddr A6:44:26:ED:AC:5F
          inet addr:192.168.3.2  Bcast:192.168.3.7  Mask:255.255.255.248
          inet6 addr: fe80::a444:26ff:feed:ac5f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:687 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

(NOTE: look at the dropped:687 packets for tap0. I don't know what that means...
other than its bad.  )

If I to a tcpdump -n -i sw2, and ping the tap0 device from my domU
instance, I see:
[root@xen xen]# tcpdump  -n  -i sw2
tcpdump: WARNING: sw2: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on sw2, link-type EN10MB (Ethernet), capture size 96 bytes
21:24:15.428994 arp who-has 192.168.3.2 tell 192.168.3.1
21:24:16.427484 arp who-has 192.168.3.2 tell 192.168.3.1
21:24:17.427558 arp who-has 192.168.3.2 tell 192.168.3.1
21:24:18.439598 arp who-has 192.168.3.2 tell 192.168.3.1
21:24:19.439673 arp who-has 192.168.3.2 tell 192.168.3.1
21:24:20.439724 arp who-has 192.168.3.2 tell 192.168.3.1

the dom0 device does not answere the ARP Who-Has request. The domU box
has the correct netmask and broadcast address defined.

I set up sw1 in a similar fashion as sw2. My two domU machine are able
to talk over sw1 just fine.

What am I missing?

Thanks - jack

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