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What is the host OS?

In my experience it is easier to either use libvirtd to control the virtual networking or run dnsmasq and configure iptables manually. I wouldnât rely on the network-nat script as it seems to only set the IP address of the vif endpoint in dom0.

Assuming you have libvirtd there are few ways of creating the virtual networking setup.

1 â Create a virtual network xml file. (The specification for the structure can be found at http://libvirt.org/formatnetwork.html). Then use the virsh command from the command line to create the virtual network. The xml file will tell libvirt to use a particular bridge and nat everything on that bridge. Additionally when vms connect to the bridge it will set up some iptables rules for you to do the forwarding from the bridge to your main network. This will require reverting your changes to the /etc/xen/xend-config.sxp

2 â Use virt-manager to configure the virtual network. This is a gui will allow you to setup the virtual networks without needed a predefined xml file. Where to go and what to click are highly dependent on the version being used as the interface has changed a lot over the fast couple years.

3 â Configure dnsmasq and iptables manually. Under the hood libvirt natâing really just sets up dnsmasq to provide dhcp, dns forwarding etc.. on the bridge interface as well as configures a few iptables rules to do the masquerading. You can configure this manually, although there is generally no need.

~Matt

From: xen-users-bounces@xxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxx] On Behalf Of Xi Shen
Sent: Thursday, April 12, 2012 9:55 AM
To: xen-users@xxxxxxxxxxxxx
Subject: [Xen-users] domU NAT network cannot connect

Hi,

I followed this guide, and started my xend service with nat-network support:

(network-script network-nat)
(vif-script vif-nat)

Then I started my domU with the following vif configure:

vif = ['ip=10.0.0.1' ]

my domU is a win7 system, and I configured the network as:

ip: 10.0.0.1
netmask: 255.255.255.0
default gateway: 10.0.0.254

dns: 8.8.8.8

I added the iptables NAT rule:

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

But my domU still cannot connect to the network.

On my dom0, "ifconfig -a" returns as follow: (note: I started the vif8.0 IF by manual)

eth0: flags=4098<BROADCAST,MULTICAST> mtu 1500

ether 00:1e:37:d2:2b:da txqueuelen 1000 (Ethernet)

RX packets 0 bytes 0 (0.0 B)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 0 bytes 0 (0.0 B)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

device interrupt 20 memory 0xfe200000-fe220000

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 16436

inet 127.0.0.1 netmask 255.0.0.0

inet6 ::1 prefixlen 128 scopeid 0x10<host>

loop txqueuelen 0 (Local Loopback)

RX packets 76637 bytes 513836706 (490.0 MiB)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 76637 bytes 513836706 (490.0 MiB)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

tap8.0: flags=4098<BROADCAST,MULTICAST> mtu 1500

ether 3e:9b:52:95:03:d3 txqueuelen 500 (Ethernet)

RX packets 2722 bytes 239183 (233.5 KiB)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 0 bytes 0 (0.0 B)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

vif8.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500

inet 10.0.0.128 netmask 255.255.255.255 broadcast 0.0.0.0

ether fe:ff:ff:ff:ff:ff txqueuelen 32 (Ethernet)

RX packets 0 bytes 0 (0.0 B)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 0 bytes 0 (0.0 B)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 576

inet 192.168.10.100 netmask 255.255.255.0 broadcast 255.255.255.255

ether 00:1f:3c:27:e6:0c txqueuelen 1000 (Ethernet)

RX packets 11301 bytes 4467424 (4.2 MiB)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 9829 bytes 1330447 (1.2 MiB)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

I am new to xen, so I might have missed some settings. Please be kind to point out.

Thank you.

--
Regardsï
David Shen

http://about.me/davidshen
https://twitter.com/#!/davidshen84

Re: [Xen-users] domU NAT network cannot connect