Brocade Communications Systems 6650 manual Ecmp load sharing for IPv6

5 ECMP load sharing for IPv6

ECMP load sharing for IPv6

The IPv6 route table selects the best route to a given destination from among the routes in the tables maintained by the configured routing protocols (BGP4, OSPF, static, and so on). The IPv6 route table can contain more than one path to a given destination. When this occurs, the Brocade device selects the path with the lowest cost for insertion into the routing table. If more than one path with the lowest cost exists, all of these paths are inserted into the routing table, subject to the configured maximum number of load sharing paths (by default 4). The device uses Equal-CostMulti-Path (ECMP) load sharing to select a path to a destination.

When a route is installed by routing protocols or configured static route for the first time, and the IPv6 route table contains multiple, equal-cost paths to that route, the device checks the IPv6 neighbor for each next hop. Every next hop where the link layer address has been resolved will be stored in hardware. The device will initiate neighbor discovery for the next hops whose link layer addresses are not resolved. The hardware will hash the packet and choose one of the paths. The number of paths would be updated in hardware as the link layer gets resolved for a next hop.

If the path selected by the device becomes unavailable, the IPv6 neighbor should change state and trigger the update of the destination in the hardware.

Brocade devices support network-based ECMP load-sharing methods for IPv6 traffic. The Brocade device distributes traffic across equal-cost paths based on a XOR of some bits from the MAC source address, MAC destination address, IPv6 source address, IPv6 destination address, IPv6 flow label, IPv6 next header. The software selects a path based on a calculation involving the maximum number of load-sharing paths allowed and the actual number of paths to the destination network. This is the default ECMP load-sharing method for IPv6.

You can manually disable or enable ECMP load sharing for IPv6 and specify the number of equal-cost paths the device can distribute traffic across. In addition, you can display information about the status of ECMP load-sharing on the device.

126	Brocade ICX 6650 Administration Guide
	53-1002600-01