Configuration Guide

Table Of Contents
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October 2021
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13. ISIS External Metric
Beginning in the software release 5.0 for the VSP 4000/7200/8000, ISIS external metrics is introduced. By
default, internal metric is always preferred over external metrics. Hence, when advertising external
networks, it is recommended to advertise these routes as external similar to what OSPF does with external
type1 and type 2. Hence, when an SPBM ISIS router decides what route to install in the route table, it will
always prefer ISIS routes with the shortest internal metric path to the SPBM node advertising them.
With this feature you can use IS-IS to:
Change the external metric-type of a route when redistributing it from another protocol to IS-IS
through route redistribution using a route-map.
Change the external metric-type of a route when accepting a remote ISIS route with the help of
ISIS accept policies using a route-map.
Match the external metric-type when redistributing ISIS routes into other protocols using the
match option in the route-map.
Match the external metric-type when accepting a remote ISIS route with the help of ISIS accept
policies by using a route-map
Process the external metric-type in the route selection process.
The IS-IS metric type can also be set using the base redistribute command without using the route map.
For configuration examples, please see the section titled “IP Shortcuts – redistribution of ISIS and OSPF”.