As a result of large traffic volume on Mgmt interfaces on the SSMs, the CMD (chassis monitor daemon) can consider the SSM1, SSM2 and the CMMs to be DOWN. In addition, a break in the communication between the different hardware components (including SSH to the SMO) can occur.
Chain of events (based on VSX mode):
- Mgmt interfaces on each SSM (per chassis), will send incoming traffic to the SMO.
- Each packet is handled by design by VS0.
- When the Mgmt interface is flooded with traffic, VS0 inbound queue can become fully utilized.
As a result, the dispatcher could not pass new packets.
- Packets coming from eth1-CIN and eth2-CIN interfaces are the keep-alive packets from different hardware components on the chassis: SSM1, SSM2, CMM1, and CMM2.
- SMO sends out the keep-alive messages (via the CIN interfaces) to the SSMs/CMMs and waits for their response.
- Due to the fully-utilized packet queue, these keep-alive packets (and SSH packets) are dropped by the dispatcher.
- CMD (chassis monitor daemon) considers the SSMs and CMMs as not available, which causes traffic outage.
Note: In VSX VSLS mode, the SMO is responsible for the chassis-monitor task.