IS-IS administrative distance

For example, if the device has a path from iBGP, from OSPF, and IPv4 IS-IS to the same destination, and all the paths are using their protocols‘ default administrative distances, the device selects the OSPF path, because that path has a lower administrative distance than the iBGP and IPv4 IS-IS paths.

The default IPv4 administrative distances on the device are:

• Directly connected - 0 (this value is not configurable)
• Static - 1 (applies to all static routes, including default routes)
• eBGP - 20
• OSPF - 110
• IPv4 IS-IS - 115
• iBGP - 200
• Local BGP - 200
• Unknown - 255 (the device will not use this route)

Lower administrative distances are preferred over higher distances. For example, if the device receives routes for the same network from IPv4 IS-IS and from iBGP, it will prefer the IPv4 IS-IS route by default.