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VLACP Packet Sequence Number Mismatch

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TitleVLACP Packet Sequence Number Mismatch
Symptoms

Intermittent VLACP Packet drops and VLACP flaps are noticed in logs:

CP1 0x000ec5d5 00000000 GlobalRouter LACP WARNING VLACP pkts sequence number mismatched. vlacpRxFrame: port X new_seq_num 27353391 old_seq_num 27353389 drop 1 total drop 733.
CP1 0x000ec5ce 04f00001.230 DYNAMIC SET GlobalRouter LACP WARNING trapSendVlacpLinkDown: Vlacp Link X is down
CP1 0x000ec5d5 00000000 GlobalRouter LACP WARNING VLACP pkts sequence number mismatched. vlacpRxFrame: port X new_seq_num 27353394 old_seq_num 27353391 drop 2 total drop 735.
CP1 0x000ec5cf 04f00001.230 DYNAMIC CLEAR GlobalRouter LACP INFO trapSendVlacpLinkUp: Vlacp Link X is up
0x000ec5d4 00000000 GlobalRouter LACP WARNING Remote Vlacp port status is down; bringing current port X/Y status down
0x000ec5ce 04f00001.192 DYNAMIC SET GlobalRouter LACP WARNING trapSendVlacpLinkDown: Vlacp Link X/Y is dow
CP1 0x0000c5eb 00300001.258 DYNAMIC SET GlobalRouter HW INFO Link Down(X/X) due to slpp
CP1   0x00000009 01900001.10 DYNAMIC SET GlobalRouter SW INFO SMLT X Link is DOWN
CP1   0x000ec5ce 04f00001.258 DYNAMIC SET GlobalRouter LACP WARNING trapSendVlacpLinkDown: Vlacp Link X/X is down
 

 

Environment
Virtual Services Platform 4000 / 7200 / 8000 / 9000 running any supported software version.
Cause

VLACP PDUs are not being received in time or out of order.

Can be for multiple reasons:
1. Issue with L1 -dirty Fiber, bad cable, port, GBIC, etc...
2. If there is a Service Provider link between two related nodes this should be checked as well.
3. Issue is due to incorrect configuration on a 3rd party device.
4. Congestion causing protocol related issues.
5. Port flaps causing loss of VLACP PDUs making the local link assume the remote link is down.
6. Configuration mismatch which causes VLACP sequence number mismatch .

Resolution

1. Review configuration for incorrect configuration.
2. Check ports for congestion.
3. Check L1 for issues.

Additional notes
Other potential reasons are listed below:
1. If there is a Service Provider link between two related nodes this should be checked as well.

2. Due to ESXi server that was sending pause frames to the edge device, slpp kicked in and brought down the links ERS edge  device  was configured in lossless mode.

"Lossless mode is mostly a mechanism for implementing symmetric flow control in a modern switched Ethernet environment.  Most vendors support asymmetric flow control by default.  With asymmetric flow control, the switch will honor the pause frame in that it will pause traffic to the device that sent the pause frame but it will not forward that pause frame.  The result is that the server is protected from being overloaded but the senders are not notified to scale back its traffic and upper layer protocols need to handle the back-off and re-transmission."

3. Port flaps might be observed due to VLACP PDU missing from the remote end, hence it will automatically shut down its own port assuming that the other port was down. Default timer is set to 500 which is good time for exchange, however we can increase the fast periodic timer to 1000 to avoid such occurrences.

NOTE: Hex value " 0x000ec5xx" indicates L1 issues.

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