Start yast2 › System › Network Settings.

Click the tab Overview and press Add.

Select Device Type Bridge. The parameter Configuration Name will be set to the next free number. Click Next.

Either use Dynamic Address (DHCP) as selected by default, or assign a static IP address to the bridge. Using Dynamic Address is only useful when also assigning a device to the bridge that is connected to some DHCP server.

If you intend to create a virtual bridge that has no connection to a real Ethernet device, use Statically assigned IP Address. In this case, it is a good idea to use addresses from the private IP address ranges, for example, 192.168.x.x or 10.x.x.x.

To create a bridge that should only serve as a connection between the different guests without connection to the host system, set the IP address to 0.0.0.0 and the netmask to 255.255.255.255. The network scripts handle this special address as an unset IP address.

Make sure that alice is shut down. Use xl commands to shut down and check.

Prepare the network configuration on the VM Host Server earth:

1. Create a hotplug interface that will be used to route the traffic. To accomplish this, create a file named /etc/sysconfig/network/ifcfg-alice.0 with the following content:

   NAME="Xen guest alice"
   BOOTPROTO="static"
   STARTMODE="hotplug"

2. Edit the file /etc/sysconfig/SuSEfirewall2 and add the following configurations:

   • Add alice.0 to the devices in FW_DEV_EXT:

     FW_DEV_EXT="br0 alice.0"

   • Switch on the routing in the firewall:

     FW_ROUTE="yes"

   • Tell the firewall which address should be forwarded:

     FW_FORWARD="192.168.1.21/32,0/0"

   • Finally, restart the firewall with the command:

     sudo systemctl restart SuSEfirewall2

3. Add a static route to the interface of alice. To accomplish this, add the following line to the end of /etc/sysconfig/network/routes:

   192.168.1.21  -  -  alice.0

4. To make sure that the switches and routers that the VM Host Server is connected to know about the routed interface, activate proxy_arp on earth. Add the following lines to /etc/sysctl.conf:

   net.ipv4.conf.default.proxy_arp = 1
   net.ipv4.conf.all.proxy_arp = 1

5. Activate all changes with the commands:

   sudo systemctl restart systemd-sysctl wicked

Proceed with configuring the Xen configuration of the VM Guest by changing the vif interface configuration for alice as described in Section 20.1, “XL—Xen Management Tool”. Make the following changes to the text file you generate during the process:

1. Remove the snippet

   bridge=br0

2. And add the following one:

   vifname=vifalice.0

   or

   vifname=vifalice.0=emu

   for a fully virtualized domain.

3. Change the script that is used to set up the interface to the following:

   script=/etc/xen/scripts/vif-route-ifup

4. Activate the new configuration and start the VM Guest.

The remaining configuration tasks must be accomplished from inside the VM Guest.

1. Open a console to the VM Guest with xl console domain and log in.

2. Check that the guest IP is set to 192.168.1.21.

3. Provide VM Guest with a host route and a default gateway to the VM Host Server. Do this by adding the following lines to /etc/sysconfig/network/routes:

   192.168.1.20 - - eth0
   default 192.168.1.20 - -

Finally, test the network connection from the VM Guest to the world outside and from the network to your VM Guest.

Shut down the VM Guest system with xl shutdown domain.

Prepare the network configuration on the VM Host Server:

1. Create a hotplug interface that will be used to route the traffic. To accomplish this, create a file named /etc/sysconfig/network/ifcfg-dolly.0 with the following content:

   NAME="Xen guest dolly"
   BOOTPROTO="static"
   STARTMODE="hotplug"

2. Edit the file /etc/sysconfig/SuSEfirewall2 and add the following configurations:

   • Add dolly.0 to the devices in FW_DEV_DMZ:

     FW_DEV_DMZ="dolly.0"

   • Switch on the routing in the firewall:

     FW_ROUTE="yes"

   • Switch on masquerading in the firewall:

     FW_MASQUERADE="yes"

   • Tell the firewall which network should be masqueraded:

     FW_MASQ_NETS="192.168.100.1/32"

   • Remove the networks from the masquerading exceptions:

     FW_NOMASQ_NETS=""

   • Finally, restart the firewall with the command:

     sudo systemctl restart SuSEfirewall2

3. Add a static route to the interface of dolly. To accomplish this, add the following line to the end of /etc/sysconfig/network/routes:

   192.168.100.1 - - dolly.0

4. Activate all changes with the command:

   sudo systemctl restart wicked

Proceed with configuring the Xen configuration of the VM Guest.

1. Change the vif interface configuration for dolly as described in Section 20.1, “XL—Xen Management Tool”.

2. Remove the entry:

   bridge=br0

3. And add the following one:

   vifname=vifdolly.0

4. Change the script that is used to set up the interface to the following:

   script=/etc/xen/scripts/vif-route-ifup

5. Activate the new configuration and start the VM Guest.

The remaining configuration tasks need to be accomplished from inside the VM Guest.

1. Open a console to the VM Guest with xl console domain and log in.

2. Check whether the guest IP is set to 192.168.100.1.

3. Provide VM Guest with a host route and a default gateway to the VM Host Server. Do this by adding the following lines to /etc/sysconfig/network/routes:

   192.168.1.20 - - eth0
   default 192.168.1.20 - -

Finally, test the network connection from the VM Guest to the outside world.