3.3. Modifying physical network configuration after installation

The initial setup of physical network hardware is done during the initial product installation. Any changes you wish to make to this base configuration after the installation must be done by logging into the XenServer Host and changing the network configuration files.

3.3.1. Hostname

Edit the /etc/sysconfig/network file to change the hostname parameter to match your system hostname.

HOSTNAME=servername

3.3.2. DNS servers

DNS servers are defined in the /etc/resolv.conf file. To add additional name-servers or change existing name-server definitions, edit the file. Name-server entries in the file have the form

nameserver 192.168.1.34
nameserver 192.168.1.33

3.3.3. Network interface configuration

Network interface configurations are defined in files stored in the /etc/sysconfig/network-scripts directory. Each network interface has its own file with the name ifcfg-device_name. There is a device file for the physical card itself and another for the Linux bridge associated with this device. For example, the first network interface card is named eth0, and its associated bridge is xenbr0, so the network configuration information would be found in the files /etc/sysconfig/network-scripts/ifcfg-eth0 and /etc/sysconfig/network-scripts/ifcfg-xenbr0.

When XenServer Host is installed on a machine with multiple NICs, only the interface selected as the management NIC will be configured with an IP address. The NIC configurations for the additional interfaces will be present in /etc/sysconfig/network-scripts directory. If you wish to use other NICs, you need to add the line

	IPADDR=<ip address>

to the appropriate ifcfg-xenbrn file

If you add a new network interface to a XenServer Host, copy an existing pair of ifcfg-ethn and ifcfg-xenbrn files and edit them appropriately.

If a network interface is configured to get its network parameters from a DHCP server, its ifcfg files might be something like the following:

	DEVICE=eth1
	ONBOOT=yes
	TYPE=Ethernet
	HWADDR=00:15:60:95:4f:d0
	BRIDGE=xenbr1
	check_link_down() { return 1 ; }

	DEVICE=xenbr1
	ONBOOT=yes
	TYPE=Bridge
	DELAY=0
	STP=off
	BOOTPROTO=dhcp
	check_link_down() { return 1 ; }

If a network interface is configured with static network parameters, it needs to have IP address, gateway, and netmask specified explicitly in its ifcfg-xenbrn file:

	DEVICE=xenbr1
	BOOTPROTO=none
	ONBOOT=yes
	TYPE=Bridge
	NETMASK=255.255.255.0
	IPADDR=10.100.2.6
	GATEWAY=10.100.2.1
	PEERDNS=yes
	DELAY=0
	STP=off
	check_link_down() { return 1 ; }

The ONBOOT tells the system to enable the network device when the computer is booted up. To disable an existing network interface, edit its ifcfg file to that the ONBOOT parameter is set to no:

	ONBOOT=no

You can also disable an existing NIC by renaming or deleting its ifcfg file.

In order to activate the configuration file changes, you will need to restart the networking service by executing service network restart from the host console, and then restarting the host agent by running xe-toolstack-restart. See Section 3.3.4, “IP address changes in Resource Pools” for further required action if the management interface has been altered.

3.3.4. IP address changes in Resource Pools

XenServer hosts in Resource Pools use a single management IP address to communicate with the other hosts in the same pool. Thus, extra care is required when changing the IP address of hosts in an existing pool.

To change the IP address of a slave host

Follow the above instructions (Section 3.3, “Modifying physical network configuration after installation”) to set the underlying network configuration files.
If the physical interface to be used as the management interface has changed, edit the /etc/xensource-inventory file on the host and alter the MANAGEMENT_INTERFACE variable to reflect the new interface used. Make sure that you use the bridge interface (e.g. xenbr0) and not the physical NIC interface in this variable.
Restart the API service on the host by executing xe-toolstack-restart.
Confirm that the slave host has successfully reconnected to the master host by running xe host-list and checking that all the other XenServer hosts in the pool are visible.

Altering the IP address of the master host is slightly more difficult, since each of the slave hosts uses its advertised IP address to communicate with it, and will not know how to contact the master if its IP address changes. Where possible, ensure that you have a dedicated IP address for a pool master which is not likely to change in the lifetime of the pool.

To change the IP address of a master host

Follow the instructions to change the IP address of a slave host (above).
When you restart the API service on the master host, all the slaves will drop into an “emergency” mode when they fail to contact the master.
On the master host, run the xe pool-recover-slaves CLI command, which will contact each of the slaves which are in emergency mode and inform them of the new IP address. Refer to the documentation on coping with pool failures (Section 2.6.2, “Master failures”) for more information.