Concept Guide

track ip route reachability
Congure object tracking on the reachability of an IPv4 route.
Syntax
track object-id ip route ip-address/prefix-len reachability [vrf vrf-name]
To return to the default setting, use the no track object-id command.
Parameters
object-id Enter the ID number of the tracked object. The range is 1 to 500.
ip-address/ prex-
len
Enter an IPv4 address in dotted decimal format. The valid IPv4 prex lengths are from /0
to /32.
vrf vrf-name (Optional) E-Series only: You can congure a VPN routing and forwarding (VRF) instance
to specify the virtual routing table to which the tracked route belongs.
Defaults none
Command Modes CONFIGURATION
Command History
Version Description
9.7(0.0) Introduced on the M I/O Aggregator.
Usage Information
Use this command to create an object that tracks the reachability of an IPv4 route. In order for a route’s
reachability to be tracked, the route must appear as an entry in the routing table.
A tracked IPv4 route is considered to match an entry in the routing table only if the exact IPv4 address and prex
length match a table entry. For example, when congured as a tracked route, 10.0.0.0/24 does not match the
routing table entry 10.0.0.0/8. If no route-table entry has the exact IPv4 address and prex length, the status of the
tracked route is considered to be DOWN.
When you congure IPv4 route reachability as a tracked object, the UP/DOWN state of the tracked route is also
determined by the entry of the next-hop address in the ARP cache. A tracked route is considered to be reachable
if there is an ARP cache entry for the route's next-hop address.
If the next-hop address in the ARP cache ages out for a route tracked for its reachability, an attempt is made to
regenerate the ARP cache entry to if the next-hop address appears before considering the route DOWN.
Related Commands
• show track – displays information about tracked objects, including conguration, current state, and clients
which track the object.
• track ip route metric threshold – congures object tracking on the threshold of an IPv4 route metric.
track resolution ip route
Congure the protocol-specic resolution value used to scale an IPv4 route metric.
Syntax
track resolution ip route {isis resolution-value | ospf resolution-value}
To return to the default setting, use the no track object-id command.
296 Object Tracking