Verifying Interface Status

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R2# show ip interface brief

Interface IP-Address OK? Method Status Protocol

Serial 0/0 172.16.23.2 YES manual up up

R2# show interface serial 0/0

Serial0/0 is up, line protocol is up Hardware is DSCC4 Serial Internet address is 172.16.23.2/24 MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usee, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation FRAME-RELAY, loopback not set Keepalive set (10 sec)

LMI enq sent 87, LMI stat recvd 88, LMI upd recvd 0, DTE LMI up LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0 LMI DLCI 102 3 LMI type is CISCO frame relay DTE FR SVC disabled, LAPF state down

Broadcast queue 0/64, broadcasts sent/dropped 23/0, interface broadcasts 210 Last input 00:00:05, output 00:00:05, output hang never Last clearing of "show interface" counters 04:22:08

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: weighted fair <output omitted>

© 2002, Cisco Systems, Inc. All rights reserved. Cisco CCIE Prep v1.0—Module 2-32

The first thing to check when troubleshooting any type of connectivity problem is the status of the interface. A brief summary of all interfaces (including subinterfaces) can be obtained by issuing the show ip interface brief command.

Table 2-8: < show ip interface brief > Command

Command

Description

show ip interface brief

Displays a brief summary of the Layer 1 and Layer 2 status of all IP interfaces on the router

To get detailed information about a specific interface, use the show interface command. Table 2-9: < show interface > Commands

Command

Description

show interface [ type ] [ number ]

Displays detailed statistics about the specified interface, including Layer 1 and 2 status, encapsulation type, and LMI information

The items to pay particular attention to in the output of this command are:

■ Make sure that the encapsulation is set to Frame Relay.

■ If the router is the Data Communication Equipment (DCE) device, make sure you are providing clocking.

■ If you are using the Local Management Interface (LMI) type of Cisco, Data-Link Connection Identifier (DLCI) 1023 should be assigned to the physical interface.

R2# show controllers serial 0/0

MK5 unit 0, NIM slot 1, NIM type code 7, NIM version 1

idb = 0x6150, driver structure at 0x34A878, regaddr = 0x810

IB at 0x6045500: mode=0x0108, local_addr=0, remote_addr=0

buffer size 1524

DCE no clock defined

R3# show controllers serial 0/0

MK5 unit 0, NIM slot 1, NIM type code 7, NIM version 1 idb = 0x6150, driver structure at 0x34A878, regaddr = 0x810 IB at 0x6045500: mode=0x0108, local_addr=0, remote_addr=0 N1=1524, N2=1, scaler=10 0, T1=1000, T3=2000, TP=1 buffer size 1524 No cable attached

© 2002, Cisco Systems, Inc. All rights reservec

A Layer 1 problem can be determined by the following output from the show interfaces command.

Serial0/0 is down, line protocol is down

Layer 1 problems can usually be tracked down to one of the following: the cable not being plugged in, wrong type of cable, bad cabling, or an interface hardware malfunction.

Most of these problems can be verified using the show controllers command.

Note If you suspect hardware or cabling problems of any kind in the actual CCIE Lab, you should notify your proctor right away.

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