Traffic loss after the ISL has been out-of-sync and keepalive is down

Symptom

Traffic loss is seen after the ISL has been out-of-sync and keepalive is down.

Cause

If the ISL becomes out-of-sync and keepalive is established, the secondary VSX LAGs are brought down. If keepalive then fails and you have split recovery mode enabled (default setting), the secondary switch brings up its VSX LAGs. This split condition leads to traffic loss because of the asymmetric traffic flow.

Action
  1. Disable split recovery mode by entering the following command on the secondary VSX switch: 
    switch(config)# vsx
switch(config-vsx)# no split-recovery
    This command shuts down the secondary link to stop the asymmetric traffic flow.
  2. Apply the same setting on the primary VSX switch for consistency and in case there is a primary/secondary role swap in the configuration.