Troubleshooting guide

5-19

ATM and Layer 3 Switch Router Troubleshooting Guide

OL-1969-02

Chapter 5 Troubleshooting Switch Router ATM Interface Connections

Using the debug Commands to Troubleshoot an Interface

The debug privileged EXEC commands can provide a wealth of information about the traffic being seen

(or not seen) on an interface.

Caution Exercise care when using debug commands. Many of these commands are processor intensive and

can cause serious network problems (such as degraded performance or loss of connectivity) if they

are enabled on an already heavily loaded switch router. When you finish using a debug command,

remember to disable it with its specific no debug command (or use the no debug all command to

turn off all debugging).

Parity Error (PE) Indicate the number of parity errors detected via

the P-bit on DS-3 links and via the BIP-8 field on

E3 links (G.832). RFC1407 defines a P-bit parity

error event as the occurrence of a received P-bit

code on the DS-3 M-frame that is not identical to

the corresponding locally-calculated code. Parity

checks detect changes to a frame during

transmission. Digital links need to retain the true

value of a frame to ensure that the destination

correctly interprets the transmitted information.

Far-End Block Error

(FEBE)

The DS-3 M-frame uses P bits to check the line's

parity. The M-subframe uses C bits in a format

called C-bit parity, which copies the result of the P

bits at the source and checks the result at the

destination. An ATM interface reports detected

C-bit parity errors back to the source via a FEBE.

Rx Cell HCS Error

(HCSE)

ATM interfaces protect against changes to the cell

header with a header error checksum (HCS) field.

The HCS detects errors only in the header and not

in the 48-byte payload. HCS errors indicate that

source, destination or ATM network corrupted the

cell header in some way.

Table 5-2 show controller Display Facilities Statistics and Explanations

Facility Statistic Explanation Recommendation