Equal Cost Multipath (ECMP) routing

In Nortel BayStack switches ECMP requires separate license. So that does it provide extra???

Many of today's businesses measure network downtime in millions of dollars per minute. With ECMP, network managers can increase the capacity of backbone trunks and virtually eliminate network downtime.

This routing mechanism enables packet routing along multiple paths with equal cost and ensures load balancing. With ECMP, a new gateway is chosen for each new source/destination IP pair. For example, one FTP connection will use only one link, but new connection to a different server will use another link.

--> The ECMP routes can be created by routing protocols (RIP or OSPF), or by adding a static route with multiple gateways.
--> The ECMP routes can be created by adding a static route with multiple gateways.

In BayStack, ECMP allows up to 4 paths to pass traffic simultaneously.

5650TD#show ip route
=========================================================
                                        Ip Route
=========================================================
DST             MASK            NEXT            COST TYPE
---------------------------------------------------------
0.0.0.0         0.0.0.0         47.152.228.1    10   IB
47.152.228.0    255.255.255.0   47.152.228.226  1    DB
Total Routes: 2
----------------------------------------------------------
TYPE Legend:
I=Indirect Route, D=Direct Route, A=Alternative Route, B=
Best Route, E=Ecmp Route, U=Unresolved Route, N=Not in HW

5650TD(config)# maximum-path 2
Access not granted.
Contact support@nortel.com to update Software license.

5650TD(config)# ip route 0.0.0.0 0.0.0.0 47.152.228.254 10
% Cannot modify settings
% ECMP: Maximum allowed IP paths already reached

Reference:
http://www.mikrotik.com/testdocs/ros/2.9/ip/route.php
http://www.networkaccess.ru/catalogue/Network_equipment/switches/nortel