Service Manual

• By the reachability of the route's next-hop router.
The UP/DOWN state of the route is 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 see if the next-
hop address appears before considering the route DOWN.
• By comparing the threshold for a route’s metric with current entries in the route table.
The UP/DOWN state of the tracked route is determined by the threshold for the current value of the route metric in the routing
table.
To provide a common tracking interface for dierent clients, route metrics are scaled in the range from 0 to 255, where 0 is
connected and 255 is inaccessible. The scaled metric value communicated to a client always considers a lower value to have
priority over a higher value. The resulting scaled value is compared against the congured threshold values to determine the
state of a tracked route as follows:
– If the scaled metric for a route entry is less than or equal to the UP threshold, the state of a route is UP.
– If the scaled metric for a route is greater than or equal to the DOWN threshold or the route is not entered in the routing
table, the state of a route is DOWN.
The UP and DOWN thresholds are user-congurable for each tracked route. The default UP threshold is 254; the default DOWN
threshold is 255. The notication of a change in the state of a tracked object is sent when a metric value crosses a congured
threshold.
The tracking process uses a protocol-specic resolution value to convert the actual metric in the routing table to a scaled metric
in the range from 0 to 255. The resolution value is user-congurable and calculates the scaled metric by dividing a route’s cost by
the resolution value set for the route type:
– For ISIS, you can set the resolution in the range from 1 to 1000, where the default is 10.
– For OSPF, you can set the resolution in the range from 1 to 1592, where the default is 1.
– The resolution value used to map static routes is not congurable. By default, Dell Networking OS assigns a metric of 0 to
static routes.
– The resolution value used to map RIP routes is not congurable. The RIP hop-count is automatically multiplied by 16 to scale
it. For example, a RIP metric of 16 (unreachable) scales to 256, which considers a route to be DOWN.
Tracking Route Reachability
Use the following commands to congure object tracking on the reachability of an IPv4 or IPv6 route.
To remove object tracking, use the no track object-id command.
1. Congure object tracking on the reachability of an IPv4 or IPv6 route.
CONFIGURATION mode
track object-id {ip route ip-address/prefix-len | ipv6 route ipv6-address/prefix-len}
reachability [vrf vrf-name]
Valid object IDs are from 1 to 65535.
Enter an IPv4 address in dotted decimal format; valid IPv4 prex lengths are from / 0 to /32.
Enter an IPv6 address in X:X:X:X::X format; valid IPv6 prex lengths are from / 0 to /128.
(Optional) E-Series only: For an IPv4 route, you can enter a VRF name to specify the virtual routing table to which the tracked
route belongs.
2. (Optional) Congure the time delay used before communicating a change in the status of a tracked route.
OBJECT TRACKING mode
delay {[up seconds] [down seconds]}
Valid delay times are from 0 to 180 seconds.
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Object Tracking