How To Configure Serial Interfaces; Configuring A Synchronous Serial Interface - Cisco 800M Series Configuration Manual

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Table Of Contents

Table of Contents

Chapter 4

Configuring the Serial Interface

Frame Relay interfaces support two types of encapsulated frames:

•

Use the encap command in PVC configuration mode to configure Cisco or IETF encapsulation on a

PVC. If the encapsulation type is not configured explicitly for a PVC, then that PVC inherits the

encapsulation type from the main serial interface.

Cisco encapsulation is required on serial main interfaces that are configured for MPLS. IETF

Note

encapsulation is not supported for MPLS.

Before you configure Frame Relay encapsulation on an interface, you must verify that all prior

Layer 3 configuration is removed from that interface. For example, you must ensure that there is no IP

address configured directly under the main interface; otherwise, any Frame Relay configuration done

under the main interface will not be viable.

LMI on Frame Relay Interfaces

The Local Management Interface (LMI) protocol monitors the addition, deletion, and status of PVCs.

LMI also verifies the integrity of the link that forms a Frame Relay UNI interface. By default, cisco LMI

is enabled on all PVCs.

If the LMI type is cisco (the default LMI type), the maximum number of PVCs that can be supported

under a single interface is related to the MTU size of the main interface. Use the following formula to

calculate the maximum number of PVCs supported on a card:

Note

The default setting of the mtu command for a serial interface is 1504 bytes. Therefore, the default

numbers of PVCs supported on a serial interface configured with cisco LMI is 186.