Core Issue
IP addresses are assigned to network interfaces to enable communication with other hosts in the network. It is common to see only a single IP address associated with an interface. However, at times it becomes necessary to configure more than one IP address on an interface.
Resolution
To configure more than one IP address on an interface, issue the ip address command with the secondary keyword in interface configuration mode. Routers configured with secondary addresses can route between the different subnets attached to the same physical interface.
For more information, refer to the Assigning Multiple IP Addresses to Network Interfaces section of Configuring IP Addressing.
