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high latency that occurred after a new line added between the branch office and HQ

Latest reply: Feb 19, 2019 07:32:35 932 1 0 0 0

Hello everyone,

Today I will share with you how to deal with the high latency that occurred after a new line added between the branch office and HQ.

topology as below:


the customer said that there was an l2vpn between the branch office and the HQ, after the new line add which directly connects the branch and HQ, the high latency occurred, when removing the backup direct connection, the service restored.

1. We suspect the service is forwarded to the lower bandwidth line, which leads the high latency.

after confirmed with the client, the direct connection line has a higher bandwidth, so when the service is normal on the MPLS L2VPN line, it wouldn’t be abnormal when a higher bandwidth line carries the service.

2. We suspect the poor quality of the backup line leads to a lot of packet loss, which results in high latency.

after check the backup line quality, the result shows the line is fine.

3. We suspect the network loop occurred.

connect up the backup line, and check the stp interface status on the branch and HQ switch, both the four interfaces are forwarding.



4. Check with the ISP, they didn’t enable the access switch to transfer the layer 2 packets transparently, after enabling the function on the access switch, the stp blocks the interface correctly.



The command l2protocol-tunnel all enable will enable the interface to transfer the layer 2 packets transparently.

That is all I want to share with you! Thank you!

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Created Feb 19, 2019 07:32:35

hope this can provide you a new thought in the troubleshooting
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