This article provides information about considerations for the Inter-chassis Link Protection ICL-PL links for the Multi-Chassis Link aggregation Group (MC-LAG).

On a Multi-Chassis LAG deployment, a LAG interface is allowed to be established across multiple MX chassis. But, firewall filters cannot be configured on the Inter-chassis Link Protection ICL-PL links. This will break the synchronization state between the MC-LAG members and can cause instabilities in the MC-LAG environment and network.

Multi-Chassis Link Aggregation Group (MC-LAG) uses Inter-Chassis Control Protocol (ICCP) to exchange control information between two MC-LAG nodes. This ICL-PL link must be used exclusively for MC-LAG synchronization state, so that no further traffic flows across these links; but information exchanged between MC-LAG members is controlled.

Additionally, no firewall filter should be configured on the ICL-PL link. Else, any filter term that could interfere on the BFD - Bidirectional Forwarding Detection, which exchanges keepalive information between the MC-LAG members or other control information state exchanged between the MC-LAG members, could lead to instability in the Multi-chassis environment.

2021-05-03: Article reviewed for accuracy; article accurate and valid