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Knowledge Base

port layer 2 atrribute is changed case MPLS tunnel down

Publication Date:  2012-07-25  |   Views:  396  |   Downloads:  0  |   Author:  z91517  |   Document ID:  EKB0000579929


Issue Description

M country N project , one commecial site NodeB service down. The topology is like attachment.  The service is PWE3 service which carried by MPLS tunnel. The NE version is V1R3C00.

Alarm Information


Handling Process

Modify NE(7-86) port layer 2 attribute from hybrid back to tag-aware, the service recover.

Root Cause

Use LSP ping from NE(7-83) to NE(7-89),it fail. Use LSP traceroute , it can reach NE(7-86).So the tunnel from NE(7-86) to NE(7-87) is down.
Check tunnel parameter, do not been modified.
Check the NE ARP list, it is found NE do not learn MAC of peer NE port. It doubt the port layer 2 attribute was modified. Because for RTN V1R3 version, the port default layer 2 attribute is tag-aware, if one NE port layer 2 attribute is modified to hybrid, it send and reply ARP frame without VLAN, so that when the peer NE port whose layer 2 attribute is tag-aware receive the ARP frame without VLAN will drop the frame.
Check two NE port layer 2 attribute, NE(7-86) is modified to hybrid.