Subnetting an IP address

Two devices on a network cannot share an IP address. Restore operations will fail if you attempt to restore an IP-based site onto a different control panel server on the same network.

To resolve the issue, you need to apply a subnet mask to the IP address. The subnet mask splits the network into two logical networks. As a result, the active backup server and the restore server still use the same IP address but now exist on separate networks.

To divide the network, you need to calculate the subnet mask that will create separate logical networks. Ensim recommends the use of a subnet mask calculator to calculate the subnet mask.

The following example explains the process of subnetting an IP address.

# Example

Assume the backup server is on the network, 192.168.1.0 and the backed up
IP-based site has an IP address, 192.168.1.1, with the netmask, 255.255.255.0.

To successfully restore the IP-based site from your active backup server onto another server in the same network, you would need to perform the following steps.

1. Use a subnet mask calculator and calculate a subnet mask to split the network into two logical networks, in our example, the subnet mask would be - 255.255.255.128.

2. Now, on the server where you want to restore the site, use the ifconfig command to configure the device with the IP address, 192.168.1.1 and the subnet mask, 255.255.255.128.

ifconfig eth0 192.168.1.1 netmask 255.255.255.128 up

where:

eth0 is the device onto which the IP based site will be restored

up causes the device to be activated

The netmask, 255.255.255.128, splits the 192.168.1.0 network into two separate subnets - 192.168.1.0 and 192.168.1.128

3. Restore the site onto the server where you want to restore the site.

4. After the site is restored, enable the site on the server, where you restored the site, using the following steps.

- Disable the site on the backup server.

- Now, shut down the device with the subnet mask, 255.255.255.128, and activate the device with the original subnet mask, 255.255.255.0.

To shut down the device, use the following command.

ifconfig eth0 192.168.1.1 netmask 255.255.255.128 down

To activate the device, use the following command.

ifconfig eth0 192.168.1.1 netmask 255.255.255.0 up

The two devices on the network now use the same IP address without attendant conflicts as a result of the logical separation of the network.