Dell S4048–ON Configuration Manual page 571

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 different 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 configured 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-configurable for each tracked route. The default UP threshold is 254; the default DOWN
threshold is 255. The notification of a change in the state of a tracked object is sent when a metric value crosses a configured
threshold.
The tracking process uses a protocol-specific 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-configurable 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 configurable. By default, Dell Networking OS assigns a metric of 0 to
static routes.
– The resolution value used to map RIP routes is not configurable. 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 configure object tracking on the reachability of an IPv4 or IPv6 route.
To remove object tracking, use the no track object-id command.
1. Configure 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 prefix lengths are from / 0 to /32.
Enter an IPv6 address in X:X:X:X::X format; valid IPv6 prefix 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) Configure 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.
The default is 0.
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Object Tracking