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 routingtable.To provide a common tracking interface for different clients, route metrics are scaled in the range from 0 to 255, where 0 isconnected and 255 is inaccessible. The scaled metric value communicated to a client always considers a lower value to havepriority over a higher value. The resulting scaled value is compared against the configured threshold values to determine thestate 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 routingtable, 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 DOWNthreshold is 255. The notification of a change in the state of a tracked object is sent when a metric value crosses a configuredthreshold.The tracking process uses a protocol-specific resolution value to convert the actual metric in the routing table to a scaled metricin the range from 0 to 255. The resolution value is user-configurable and calculates the scaled metric by dividing a route’s cost bythe 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 tostatic routes.– The resolution value used to map RIP routes is not configurable. The RIP hop-count is automatically multiplied by 16 to scaleit. For example, a RIP metric of 16 (unreachable) scales to 256, which considers a route to be DOWN.Tracking Route ReachabilityUse 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 modetrack 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 trackedroute belongs.2. (Optional) Configure the time delay used before communicating a change in the status of a tracked route.OBJECT TRACKING modedelay {[up seconds] [down seconds]}Valid delay times are from 0 to 180 seconds.The default is 0.Object Tracking 571
