Q: What is Equal Cost Multi Path (ECMP) on Mobility Access Switch?
A: Equal Cost Multipath (ECMP) enables Mobility Access Switch to forward the data packets to any of the multiple nexthops of a routing destination. The route manager identifies the best routing destination based on the priority of the protocol. After the route manager identifies the best route, all the nexthops of that route are used for datapath forwarding. ECMP is auto-enabled and does not require any command to enable it.
ECMP provides flow-based load balancing for the chosen routing destination. For a given flow same nexthop is used to forward all the packets. For multiple flows, load balancing happens across multiple nexthops. ECMP uses the source IP and destination IP to define a flow. For TCP/UDP packets, it also uses the source and destination ports to define the flow. ECMP automatically load balances the traffic when multiple nexthops with equal cost exist
Apart from multiple nexthops, ECMP also enables addition of metric for a route. ECMP nexthops are per metric basis. For a given metric, there can be multiple nexthops (up to 4). A route with a lower metric is added to the route manager. The higher metric routes are added only when the lower metric routes are deleted.
This option is enabled by default.