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Chapter 7

Troubleshooting Serial Line and Frame Relay Connectivity

Problems can be detected by watching the number of FECN or BECN

packets increase, which indicates line congestion. Forward explicit
congestion notification, FECN, notifies the receiving station (DTE) that
congestion was experienced en route to the destination. Backward
explicit congestion notification, BECN, notifies the sending station that
congestion was experienced. FECN messages are sent in the direction of
the congestion, and BECN messages are sent in the opposite direction
of the congestion.

show frame-relay map

The show frame-relay map command contains information about the
DLCI numbers and the encapsulation of all Frame Relay interfaces. The
status of the interface is indicated with the up or down state found within the
parentheses. The next field indicates the type of interface: point-to-point or
multipoint. The DLCI for the interface and the encapsulation type are also
included in the output. Here is a sample:

Router_B#show frame-relay map

Serial0.10 (down): point-to-point dlci, dlci
24(0x18,0x480), broadcast, IETF, BW = 1024000 status
defined, inactive

Serial0.7 (down): point-to-point dlci, dlci
21(0x15,0x450), broadcast, IETF, BW = 1024000 status
defined, inactive

Serial0.5 (up): point-to-point dlci, dlci 20(0x14,0x440),
broadcast, IETF, BW = 1024000 status defined, active

Serial0.6 (up): point-to-point dlci, dlci 30(0x1E,0x4E0),
broadcast, IETF, BW = 48000 status defined, active

Serial0.4 (up): point-to-point dlci, dlci 18(0x12,0x420),
broadcast, IETF, BW = 1024000 status defined, active

Serial0.2 (up): point-to-point dlci, dlci 27(0x1B,0x4B0),
broadcast, IETF, BW = 48000 status defined, active

Serial0.11 (up): point-to-point dlci, dlci 31(0x1F,0x4F0),
broadcast, IETF, BW = 48000 status defined, active

Serial0.9 (up): point-to-point dlci, dlci 29(0x1D,0x4D0),
broadcast, IETF, BW = 48000 status defined, active

Serial0.12 (up): point-to-point dlci, dlci 32(0x20,0x800),
broadcast, IETF, BW = 48000 status defined, active

Serial0.8 (up): point-to-point dlci, dlci 28(0x1C,0x4C0),
broadcast, IETF, BW = 48000 status defined, active

Serial1.1 (up): point-to-point dlci, dlci 16(0x10,0x400),
broadcast, IETF, BW = 1024000 status defined, active

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