Configuring Principles for Using Equal-Cost IPv6 IS-IS Routes
Context
If there are redundant IS-IS links, multiple routes may have an equal cost.
Configure load balancing for equal-cost IS-IS routes so that traffic will be evenly balanced among these links. This mechanism increases the link bandwidth usage and prevents network congestion caused by link overload. However, this mechanism may make traffic management more difficult because traffic will be randomly forwarded.
Procedure
- Configure equal-cost IS-IS routes to work in load-balancing
mode.
- Run ipv6 maximum load-balancing number
The maximum number of load-balancing equal-cost IPv6 IS-IS routes is set.
By default, the AR100&AR120&AR150&AR160&AR200 series, AR1200 series, AR2201-48FE, AR2202-48FE, AR2204-27GE, AR2204-27GE-P, AR2204-51GE-P, AR2204-51GE, AR2204-51GE-R, AR2204E, AR2204E-D, AR2204 support a maximum of four equal-cost routes, and the AR2220, AR2220E, AR2204XE, AR2240 (using SRU40, SRU60, SRU80, SRU100E), AR2240C, AR3600 (using SRUX5), and AR3200 (using SRU40, SRU60, SRU80, SRU100E) series support a maximum of eight equal-cost routes, AR2240 (using SRU200, SRU200E or SRU400), and AR3200 (using SRU200, SRU200E or SRU400) series support a maximum of sixteen equal-cost routes.
When the number of equal-cost routes is greater than number specified in the ipv6 maximum load-balancing command, valid routes are selected for load balancing based on the following criteria:- Route preference: Routes with higher preferences are selected for load balancing.
- Interface index: If routes have the same priorities, routes with higher interface index values are selected for load balancing.
- Next hop IP address: If routes have the same priorities and interface index values, routes with larger IP address are selected for load balancing.
- Run ipv6 maximum load-balancing number
