FreeBSD® Unleashed

Creating IP Aliases

There's nothing to stop you from assigning as many IP addresses as you want to an Ethernet card. Recalling our discussion of ARP from the previous chapter, a new TCP/IP connection looks up a LAN host by its IP address, asking for the MAC address of whatever Ethernet interface has that IP address. It doesn't do the reverse. One MAC address can answer for many different IP addresses, but one IP address can't be assigned to multiple Ethernet cards without errors and collisions resulting.

The way to assign multiple IP addresses to a single card is through IP aliasing. As with the route command, every platform does aliasing slightly differently; syntax varies from system to system. On FreeBSD, alias is used as a keyword to ifconfig ...