Physical versus virtual router interfaces

The two types of router interfaces correspond to the two types of routing supported by Passport 1000 Series routing switches:

• Physical router interfaces (also called isolated router interfaces) correspond to routing on a physical port (also called routing on an isolated routing port). Any port on the routing switch can be configured to be an isolated routing port. In this mode, the port only routes IP traffic and does not perform any bridging. The IP address is assigned to the port itself, and the router interface servicing the isolated routing port is called a physical router interface. Note that there is a one-to-one correspondence between the physical port and the router interface.
• Virtual router interfaces correspond to routing on a virtual port that is associated with a VLAN. This type of routing is the routing of IP traffic to and from a VLAN. Because a given port can belong to multiple VLANs (some of which are configured for routing on the switch and some of which are not), there is no longer a one-to-one correspondence between the physical port and the router interface. For VLAN routing, the router interface for the VLAN is called a virtual router interface because the IP address is assigned to an interface on the routing entity in the switch. This initial interface has a one-to-one correspondence with a VLAN on any given switch.

In a Passport 1000 Series routing switch, the IP address of any physical or virtual router interface can be used for IP-based network management (SNMP, Telnet, and Web).