Configuring Principles for Using Equal-Cost IS-IS Routes
Context
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.
Configure preference values for equal-cost IS-IS routes so that only the route with the highest preference will be used and the others function as backups.
This configuration facilitates traffic management and improves the network reliability, without the need to change original configurations.
Procedure
- Configure equal-cost IS-IS routes to work in load-balancing mode.
- Run maximum load-balancing number
The maximum number of load-balancing equal-cost IS-IS routes is set.
By default, load balancing is supported and a maximum of 128 equal-cost routes can participate in load balancing.
When the number of equal-cost routes is greater than number specified in the 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 maximum load-balancing number
- Configure preference values for equal-cost IS-IS routes.
