3troubleshootingjunos

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Physical Int rface Troubleshooting

To troubleshoot Frame lay, verify whether the problem is on the physical port or the

virtual circuit. You can troubleshoot using loops to determine where the problem lies.

To verify the physical port, use the show interfaces extensive command and

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ensu e that no SONET/SDH, E3 and T3, or E1 and T1 alarm is present. If more than

one logical interface is configured, they will typically all be down if the port, cable, or

CSU/DSU device is faulty.

L gical Interface Troubleshooting

For problems on the logical interface level (that is, virtual circuit), check for the

following:

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Mismatched LMI type;

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Incorrectly set encapsulation on one of the routers;

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Correctly configured DLCI values;

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DLCI-to-logical interface assignment; and

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If keepalives are sending and receiving.

You should use the show interfaces brief command to verify settings, LMI

type, and packets sent and received. (LMI provides keepalive functionality in Frame

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Physical Interface Troubl shooting

The approach for troubl

shooting ATM is similar to that for Frame Relay—verify

whether the problem is

the physical port or the virtual circuit. To verify the physical

port, use the show interfaces extensive command, and ensure that no

for

SONET/SDH, E3 or T3, or alarm is present. If more than one logical interface is

configu ed, they will typically all be down if the port, cable, or CSU/DSU device is

faulty.

Y u also can use loopback testing to determine where the problem lies.

Logical Interface Troubleshooting

For problems on the logical interface level (that is, the virtual circuit), check for the

following:

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Correct operation of the Integrated Local Management Interface (ILMI)

protocol, if enabled;

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Correct VPI and VCI;

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Operation of the Layer 2 ATM virtual circuit without requiring (or involving)

IP functionality by using the ATM-based ping command; and

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Correct VPI and VCI to logical interface mappings.

vpi 0 {

maximum-vcs 200;

}

}

ilmi;

unit 0 {

vci 100;

oam-period 10;

oam-liveness {

up-count 3;

down-count 3;

}

family inet {

address 10.0.16.1/24;

}

}

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show interfaces brief: Includes VPI, VCI, and DLCI values for

logical interfaces, including status and keepalive settings.

•

show interfaces detail: Includes multipoint VPI and VCI to IP

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Reproductionaddress mappings.

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functional through the use of s

gm nt or end-to-end F5 (VC level) OAM cell flows. The

key point is that these pings do not involve IP or ICMP, and, as such, are used to test

the ATM layer itself. As shown

the slide, a segment-level ATM ping is returned by the

device te minating that VC segment; typically this device is the ingress ATM switch

po t, as shown in the case of Platform 2. In contrast, the end-to-end switch causes

the OAM cells toReproductionloop by the device, which terminates the VC, as shown in the case of

Plat rm 1 and Platform 3.

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Case Study

The slide highlights the topic we discuss next.

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Interface Troubl shooting Flowchart

The purpose of the int

rface troubl shooting flow chart shown on the slide is simply to

provide a set of high-l

v l st ps and decision points designed to get you started on the

path of interface and transmission line troubleshooting. Note that reasonable people

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might disag ee the exact ordering of the steps or on the particulars of the CLI

commands that could be used to help isolate an interface or circuit problem.

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