IP Routing Features

Configuring Static IP Routes

�Null (reject) – the static route consists of the destination network address and network mask, and the reject parameter. Typically, the null route is configured as a backup route for discarding traffic if the primary route is unavailable.

Static IP Route Parameters

When you configure a static IP route, you must specify the following param­ eters:

�The IP address and network mask for the route’s destination network.

�The route’s path, which can be one of the following:

•The IP address of a next-hop gateway

•A “null” interface. The routing switch drops traffic forwarded to the null interface.

You also can specify the following optional parameters:

�The route’s metric – The value the routing switch uses when comparing this route to other routes in the IP route table to the same destination. The metric applies only to routes that the routing switch has already placed in the IP route table. The default metric for static IP routes is 1.

�The route’s administrative distance – The value that the routing switch uses to compare this route with routes from other route sources to the same destination before placing a route in the IP route table. This param­ eter does not apply to routes that are already in the IP route table. The default administrative distance for static IP routes is 1.

The default metric and administrative distance values ensure that the routing switch always prefers static IP routes over routes from other sources to the same destination.

Static Route States Follow Port States

IP static routes remain in the IP route table only so long as the next-hop gateway, port, or virtual interface used by the route is available. If the gateway or port becomes unavailable, the software removes the static route from the IP route table. If the gateway or port later becomes available again, the software adds the route back to the route table.

This feature allows the routing switch to adjust to changes in network topology. The routing switch does not continue trying to use routes on unavailable paths but instead uses routes only when their paths are available.

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