Equal Cost Multipath

Table 1. Equal Cost Multiple Path for IPv4 product support
Feature	Product	Release introduced
Equal Cost Multiple Path (ECMP) for IPv4	5320 Series	Fabric Engine 8.6 Only 5320-48P-8XE and 5320-48T-8XE support more than one VRF with IP configuration.
	5420 Series	VOSS 8.4
	5520 Series	VOSS 8.2.5
	5720 Series	Fabric Engine 8.7
	7520 Series	Fabric Engine 8.10
	7720 Series	Fabric Engine 8.10
	VSP 4900 Series	VOSS 8.1
	VSP 7400 Series	VOSS 8.0

With Equal Cost Multipath (ECMP), the switch can determine up to eight equal-cost paths to the same destination prefix. You can use multiple paths for load sharing of traffic. These multiple paths provide faster convergence to other active paths in case of network failure. By maximizing load sharing among equal-cost paths, you can use links between routers more efficiently when sending IP traffic. Equal Cost Multipath is formed using routes from the same source or protocol.

All IP ECMP routes that share the same combination of ECMP next hops consume the same ECMP group resource. The following list illustrates how shared next hops affect resource consumption:

Prefix 3.1.1.0/16 is learned as an ECMP route with next hops A and B, and consumes one entry in the ECMP GROUP table.
Prefix 4.1.1.0/16 is learned as an ECMP route with the same next hops, A and B. No additional resource is taken in the ECMP GROUP table.
Prefix 5.1.1.0/16 is learned as an ECMP route with next hops B and C, and consumes one additional entry in the ECMP GROUP table.

ECMP is supported on both the Global Routing Table (GRT) and Virtual Routing and Forwarding (VRF).

The ECMP feature supports and complements the following protocols and route types:

Border Gateway Protocol (BGP)
Default route
Intermediate System-to-Intermediate System (IS-IS)
Open Shortest Path First (OSPF)
Routing Information Protocol (RIP)
Static route
VRF

ECMP Pathlist

Use the ECMP Pathlist feature to control how many equal-cost paths to add to the routing manager for the same destination.