The command used to redistribute routes into IS-IS supports a parameter called metric-type, which can take one of two values: internal or external. In releases that do not support the external metric type, the routes are always advertised into IS-IS as internal, irrespective of whether you configure the metric-type to internal or external. The saved configuration itself correctly shows the value that you selected.
If the configuration file has redistribution commands that set the metric-type to external, after you upgrade to a release that supports the external metric type, the routes will be advertised into IS-IS as external routes. This constitutes a change in how the routes are advertised into IS-IS after the upgrade as compared to before the upgrade. This configuration can cause unintended traffic issues if the other switches in the network are not yet upgraded to a release that recognizes external routes in IS-IS.
To know which release supports the external metric type on your platform, see VOSS Release Notes for interoperability considerations.
To avoid unintentionally impacting traffic immediately following an upgrade, as a best practice, check the existing IS-IS redistribution configuration of a switch to determine if the metric-type is set to external in the redistribution commands. If metric-type external is not used in the redistribution, the switch can be upgraded using the normal upgrade procedures. If the metric-type external is used with any redistribution command, change it to internal, and then save the configuration. After this the switch can be upgraded using the normal upgrade procedures.
Switch:1(config-isis)#show ip isis redistribute [vrf WORD<1-16>] ================================================================================ ISIS Redistribute List - GlobalRouter ================================================================================ SOURCE MET MTYPE SUBNET ENABLE LEVEL RPOLICY -------------------------------------------------------------------------------- RIP 0 internal allow TRUE l1 OSPF 0 external allow TRUE l1 LOC 0 external allow TRUE l1
router isis
isis redistribute <protocol> metric-type internal
save config
The protocol above could be one of the following: direct, ospf, static, rip or bgp.
router vrf WORD<1-16>
isis redistribute <protocol> metric-type internal
save config
The protocol above could be one of the following: direct, ospf, static, rip or bgp.