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ECC subnet size cause frequent LAG_DOWN and LAG_MEMBER_DOWN alarms on RTN 950

Publication Date:  2019-07-09 Views:  229 Downloads:  2

Issue Description

Topology consists of 3 RTN 950 nodes, V1R2, in chain configuration.
Between nodes, there are XPIC microwave links and the two polarizations of each direction are configured with LAG.

Suddenly LAG_DOWN and LAG_MEMBER_DOWN alarms started to occur intermittently (~150 occurrences in 24 hours).

Alarm Information

LAG_DOWN is triggered when LAG doesn't have any active members. All LAG members report LAG_MEMBER_DOWN alarm.

LAG_MEMBER_DOWN returned: 0x00 0x06 0xff 0x00 0x01 0x02 meaning that member port failed to receive LACP packets.

Handling Process

Found that ECC subnet was too big, each site had routes toward more than 300 elements. This can be verified on NE ECC link management, or with navigator :cm-get-coreroute; (attached navigator.txt)

In order to reduce ECC subnet size, we changed ECC Extended mode from Auto to Specified, on GNE.

Root Cause

1. Checked microwave link configuration -- It was consistent, see attach
2. Checked LAG configuration to be consistent --  It was consistent, see attach
3. Checked status of ECC Extended & NE ECC link management -- Found too many routes in ECC link management, see navigator.txt


LACP packets and DCN packets were sharing the same resources (microwave internal communication channel and board processing power). Because the ECC subnet was too big, resources of RTN were consumed to process DCN packets and some LACP packets were delayed. Because LACP packet was not processed on time, LACP_MEMBER_DOWN alarm was triggered.

After we reduced subnet size, alarms didn't reoccur.