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the customer feedback the traffic latency is very high

Publication Date:  2019-04-11 Views:  57 Downloads:  0

Issue Description

the customer feedback the traffic latency is very high.



the link between SW2 and SW4 is a mpls l2vpn, it works as a backup link.

Handling Process

1.checking on the PC, found that it's normal to ping the server, ping delay seems OK.

2.confirm with customer, in which situation will the latency raise too high. the customer feedback it is irregular.

3.confirm with customer, we learn that the main traffic will be transfered on the link between sw3 and sw2, the l2vpn link which connect the sw4 and sw2 works as the backup line. we suspect the traffic may be forwarded to the l2vpn link rather than directly connection link, and the poor bandwidth is used out causing the latency raise too high.

4.check the routing table on the sw3 and sw4, the result verify the suspection.

Root Cause

the ISIS is implemented between sw2, sw3 and sw4, sw2 and sw3 establish the L2 neighbor relationship, sw2 and sw4 establish L1 neighbor relationship, this cause the traffic are forwarded to the sw4, then sw2. But the l2vpn link owns the poor bandwidth, when the bandwidth resource used out, the latency raise too high.


adjust the ISIS setting, modify the circuit type between sw2 and sw3 to level 1, so that the sw2 and sw3 could establish L1 neighbor relationship. After that, the service get right.