Resilient/Consistent Hashing for LAG Group

Resilient hashing is supported by link aggregation groups (LAGs) and equal cost multipath (ECMP) sets on specified platforms. A LAG combines Ethernet interfaces (members) to form a logical point-to-point link that increases bandwidth, provides reliability, and allows load balancing. Resilient hashing enhances LAGs by minimizing destination remapping when a new member is added to or deleted from the LAG. Resilient hashing works in conjunction with the default static hashing algorithm. It distributes traffic across all members of a LAG by tracking the flow's LAG member utilization. When a flow is affected by a LAG member change, the Packet Forwarding Engine rebalances the flow by reprogramming the flow set table. Destination paths are remapped when a new member is added to or existing members are deleted from a LAG. Resilient hashing applies only to unicast traffic and supports a maximum of 1024 LAGs, with each group having a maximum of 256 members. An ECMP group for a route contains multiple next-hop equal cost addresses for the same destination in the routing table. (Routes of equal cost have the same preference and metric values.) A hash algorithm is used to choose one of the next-hop addresses in the ECMP group to be installed in the forwarding table. Flows to the destination are rebalanced using resilient hashing. Resilient hashing enhances ECMPs by minimizing destination remapping when a new member is added to or deleted from the ECMP group.