Interface Descriptors

When you configure an interface, you are effectively specifying the properties for a physical interface descriptor. In most cases, the physical interface descriptor corresponds to a single physical device and consists of the following parts:

• The interface name, which defines the media type
• The slot in which the FPC is located
• The location on the FPC in which the PIC is installed
• The PIC port
• The interface's channel and logical unit numbers (optional)

Each physical interface descriptor can contain one or more logical interface descriptors. These allow you to map one or more logical (or virtual) interfaces to a single physical device. Creating multiple logical interfaces is useful for ATM, Frame Relay, and Gigabit Ethernet networks, in which you can associate multiple virtual circuits, data-link connections, or VLANs with a single interface device.

Each logical interface descriptor can have one or more family descriptors to define the protocol family that is associated with and allowed to run over the logical interface. The following protocol families are supported:

• Internet Protocol, version 4 (IPv4)
• Internet Protocol, version 6 (IPv6)
• Circuit cross-connect (CCC)
• Translational cross-connect (TCC)
• International Organization for Standardization (ISO)
• Multilink Frame Relay End-to-End (MLFR End-to-End)
• Multilink Frame Relay UNI NNI (MLFR UNI NNI)
• Multilink PPP (MLPPP)
• Multiprotocol Label Switching (MPLS)
• Trivial Network Protocol (TNP)
• Virtual Private LAN Service (VPLS)

Finally, each family descriptor can have one or more address entries, which associate a network address with a logical interface and hence with the physical interface.

You configure the various interface descriptors as follows:

• You configure the physical interface descriptor by including the interfaces interface-name statement.
• You configure the logical interface descriptor by including the unit statement within the interfaces interface-name statement or by including the .logical descriptor at the end of the interface name, as in ge-0/0/0.1, where the logical unit number is 1.
• You configure the family descriptor by including the family statement within the unit statement.
• You configure address entries by including the address statement within the family statement.
• You configure tunnels by including the tunnel statement within the unit statement.