How do I add multiple network adapters to a virtual machine?

Symptom

When creating a virtual machine with multiple networks attached, the virtual machine console shows multiple network adapters but no IP addresses.

Cause

Each network corresponds to one network adapter on the virtual machine. Attaching a network to a virtual machine is equivalent to inserting a physical network card into a server. Running the ifconfig command shows the eth devices. If no IP address appears, the network adapter is not configured correctly.

Solution

1. Create a configuration file for the new network adapter by following the eth0 configuration file as a template. The following example applies to a CentOS 7.2 environment. Paths and files may differ for other Linux versions:

2. Run the following commands in the console to copy the eth0 configuration file:

   # Replace eth0 with eth1 in the configuration file, and delete the UUID entry
   cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth1
   sed -i 's/eth0/eth1/g' ifcfg-eth0
   sed -i '/UUID*/d' /etc/sysconfig/network-scripts/ifcfg-eth1

3. Restart the network to apply the changes:

   /etc/init.d/network restart

4. Run the ifconfig command to verify that the new network adapter shows an IP address. To attach additional networks to the virtual machine, repeat the steps above.