IS-IS Error Logging

The errors logged by Cisco IOS Software frequently provide information about problems occurring on the router or the network in general and should always be checked for pertinent clues when troubleshooting problems. Example 10-42 shows an IS-IS- related logged error that indicates that an address prefix that had a length of 135 bytes was detected , which is more than the expected maximum size . This log information also provides the ID of the LSP carrying the malformed TLV with the bad information. Example 10-43 shows that a hello packet is received from an ATM VC with a length of 51 bytes rather than the expected 53 bytes.

Example 10-44 shows information logged for an adjacency change.

Example 10-42 IS-IS Logging for Malformed Packets on PoS Link

 Mar 10 11:59:46.171: %CLNS-3-BADPACKET: ISIS: L1 LSP, option 1 address prefix   length 135 > max NSAP length (21), ID 0000.0000.04B7.00-00, seq 25948, ht 1115   from *PPP* (POS6/0). 

Example 10-43 IS-IS Logging for Malformed Packet on ATM PVC

 Nov 16 02:18:04.848 EDT: %CLNS-4-BADPACKET: ISIS: P2P hello, option 8 length 53   remaining bytes (51) from VC 2 (ATM4/0.2) 

Example 10-44 Logs for Adjacency Changes

 RT1#  show log  %CLNS-5-ADJCHANGE: ISIS: Adjacency to 0000.0000.0001 (ethernet 0)  %CLNS-5-ADJCHANGE: ISIS: Adjacency to 0000.0000.0002 (ethernet 0)