Users 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
9.8(0.0P5) Introduced on the S4048-ON.
9.8(0.0P2) Introduced on the S3048-ON.
9.7(0.0) Introduced on the S6000-ON.
8.3.12.0 Introduced on the S4810.
8.4.1.0 Introduced.
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.
1020
Object Tracking