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Knowledge Base

TMGs Became Out of Service Because One Member Interface in IP-Trunk Was Faulty

Publication Date:  2019-07-04  |   Views:  338  |   Downloads:  0  |   Author:  00178210  |   Document ID:  ETC0001085519


Issue Description

TMG 1 and TMG 3 connecting to AR 1 and AR 2 were out services. At the same time, the LDP sessions were interrupted for 35 minutes according to information on the routers.

On the square-shaped network, TMG 2 was normal but diagonal TMG 1 and TMG 3 were out of services.

The traffic model was as follows:

UMG1->YYAR1->YYAR2->XXBR2->XXAR4->XXSS, diagonal

UMG2->YYAR1->YYAR2->XXBR2->XXAR4->XXSS, on the same plane

UMG3->YYAR2->YYAR1->XXBR1->XXAR3->XXSS, diagonal

1. At 9:37:38, pos5/0/0 on AR 1 was down because the receive optical power was lower than the lower threshold.

Sep  5 2009 09:37:38 GDHIZ-BA-IPNET-RT01-NE80E %%01SRM/4/ESFP_RXPOWER_LOW(l): Slot5 PIC0 port0 ESFP RxPower is too low, maybe fiber not plugged.

Sep  5 2009 09:37:38 GDHIZ-BA-IPNET-RT01-NE80E %%01SRM/4/PICP1RXCDRERR(l): Slot5 PIC0 SERDES receive CDR is abnormal, maybe fiber not plugged.

2. At 9:38:33, undo ip-trunk 2 was applied to pos 11/0/0.

Sep  5 2009 09:38:33 GDHIZ-BA-IPNET-RT01-NE80E %%01SHELL/5/CMDRECORD(l): Record command information.
(Task=vt1, Ip=, User=lh13802881520, Command="undo ip-trunk 2")

3. The ip-trunk 2 interface was down because least active-linknumber 2 had been applied to ip-trunk2.

interface Ip-Trunk2
description TO-[xxxx-RT02-NE80E]IP-trunk3-3*10G
least active-linknumber 2
Sep  5 2009 09:38:33 GDHIZ-BA-IPNET-RT01-NE80E %%01TRUNK/5/TRUNKDOWN(l): The status of interface Ip-Trunk2 turns Down.

4. At 9:38:52, the LDP session connected to AR 2 was interrupted.

Sep  5 2009 09:38:52 GDHIZ-BA-IPNET-RT01-NE80E %%01LDP/4/HOLDTMREXP(l):
Sessions were deleted because the hello hold timer expired. (PeerId=x.x.209.18)

5. At 9:38:55, P5/0/0 recovered and IP-trunk2 became up. The ISIS peers for AR 1 and AR 2 also became up.

Sep  5 2009 09:38:55 GDHIZ-BA-IPNET-RT01-NE80E %%01TAD/4/IFUP(l):-Slot=5; Owing to the alarm message(s), Pos5/0/0 went Up.
Sep  5 2009 09:38:55 GDHIZ-BA-IPNET-RT01-NE80E %%01TRUNK/5/MEMBER_UP(l): The status of the trunk member turns Up. (TrunkName=Ip-Trunk2, PortName=Pos5/0/0)
Sep  5 2009 09:38:55 GDHIZ-BA-IPNET-RT01-NE80E %%01ISIS/4/ADJ_CHANGE(l): The neighbor of ISIS was changed. 
(IsisProcessId=1, Neighbor=2211.3020.9018, InterfaceName=Ip-Trunk2, CurrentState=up, ChangeType=3_WAY_UP)

6. At 10:13:16, ip-trunk 2 was configured for pos 11/0/0.

Sep  5 2009 10:13:17 GDHIZ-BA-IPNET-RT01-NE80E %%01TRUNK/5/MEMBER_UP(l):-Slot=11; The status of the trunk member turns Up. (TrunkName=Ip-Trunk2, PortName=Pos11/0/0)
Sep  5 2009 10:13:16 GDHIZ-BA-IPNET-RT01-NE80E %%01SHELL/5/CMDRECORD(l): Record command information. (Task=vt1, Ip=, User=lh13802881520, Command="ip-trunk 2")

7. At 10:13:23, the LDP session connected to AR 2 was up.

#Sep  5 10:13:23 2009 GDHIZ-BA-IPNET-RT01-NE80E LDP/4/SessionUp: Session( public Instance)'s state change to Up

Handling Process

In the scenario in which the IP-Trunk between an AR and a BR contained multiple links, some protocols may be hashed to an incorrect link if link quality is poor or a link is interrupted. This is because IP-Trunk cannot sense packet loss at trunk members without using additional protocols.

Root Cause

One link in the IP-Trunk was faulty, resulting in interruption of some protocols.


Disable the faulty interface and add it to the IP-Trunk after the fault is rectified.


1. In a loopback test or incorrect optical fiber connection, the link POS alarm function does not take effect because the optical line is normal. BFD for trunk must be deployed. Each member interface runs an independent BFD process. In this way, the interface status can be determined according to the BFD status. The BFD packet transmission interval and detection multiplier are configurable. NE40E, NE80E, and NE5000E support deployment of BFD.

2. IP-trunk cannot perform LCP and IPCP negotiation using POS interfaces. If an interface is faulty, the protocol on the interface becomes down without affecting protocols on other interfaces.