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Configure Priorities for IPv4 IS-IS Routes

Latest reply: Dec 25, 2018 02:43:43 910 2 10 0 0


As we know, when a routing table has a large number of routing entries on an IS-IS device, it takes a long time to implement the SPF calculation on the device. The prefix-priority command can be used to allow some key routes to be preferentially calculated.

The convergence priorities of IS-IS routes can be critical, high, medium, and low. The priorities are listed in descending order.

The convergence priority of IS-IS routes is used as follows:

l  For the existing IS-IS routes, IS-IS resets the convergence priority for the routes based on the prefix-priority command.

l  For the newly added IS-IS routes, IS-IS sets the convergence priority for the routes based on the filtering result of the prefix-priority command.

l  If an IS-IS route matches the matching rules of multiple convergence priorities, the highest convergence priority is used.

l  If an IS-IS route matches tags of multiple convergence priorities, the highest convergence priority is used.

l  If the route level is not specified, IS-IS configures convergence priorities for both Level-1 routes and Level-2 routes.

If we need to configure the priority of a route, you can first label the route and then set the priority of the label in IS-IS.

The configuration example is as below:

interface loopback 0
isis tag-value 100
isis 1
prefix-priority level-2 high tag 100

That's all for the example.

If you have any further questions, kindly let us know.

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Created Dec 25, 2018 01:06:51

You can describe the priority of configuring IPv6 IS-IS routes.
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Created Dec 25, 2018 02:43:43

How many level is there in IS-IS protocol? I will check on that later, seems a important parameter.
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