Static Route States Follow Port States - Brocade Communications Systems FastIron SX 800 Configuration Manual

Configuring IP parameters - Layer 3 switches
You also can specify the following optional parameters:
• The metric for the route - The value the Layer 3 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 Layer 3 switch has already placed in the IP route table. The
default metric for static IP routes is 1.
• The administrative distance for the route - The value that the Layer 3 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 parameter 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 Layer 3 switch always prefers static IP routes over routes from
other sources to the same destination.
Multiple static routes to the same destination provide load sharing and redundancy
You can add multiple static routes for the same destination network to provide one or more of the following benefits:
• IP load balancing - When you add multiple IP static routes for the same destination to different next-hop gateways, and the
routes each have the same metric and administrative distance, the Layer 3 switch can load balance traffic to the routes'
destination.
• Path redundancy - When you add multiple static IP routes for the same destination, but give the routes different metrics or
administrative distances, the Layer 3 switch uses the route with the lowest administrative distance by default, but uses another
route to the same destination if the first route becomes unavailable.

Static route states follow port states

IP static routes remain in the IP route table only so long as the port or virtual interface used by the route is available. If the port or virtual
routing interface becomes unavailable, the software removes the static route from the IP route table. If the port or virtual routing interface
becomes available again later, the software adds the route back to the route table.
This feature allows the Layer 3 switch to adjust to changes in network topology. The Layer 3 switch does not continue trying to use
routes on unavailable paths but instead uses routes only when their paths are available.
The static route is configured on Switch A, as shown in the CLI example following the figure.
FIGURE 5 Example of a static route
The following command configures a static route to 10.95.7.0, using 10.95.6.157 as the next-hop gateway.
device(config)# ip route 10.95.7.0/24 10.95.6.157
When you configure a static IP route, you specify the destination address for the route and the next-hop gateway or Layer 3 switch
interface through which the Layer 3 switch can reach the route. The Layer 3 switch adds the route to the IP route table. In this case,
Switch A knows that 10.95.6.157 is reachable through port 1/1/2, and also assumes that local interfaces within that subnet are on the
same port. Switch A deduces that IP interface 10.95.7.188 is also on port 1/1/2.
The software automatically removes a static IP route from the IP route table if the port used by that route becomes unavailable. When the
port becomes available again, the software automatically re-adds the route to the IP route table.
64
FastIron Ethernet Switch Layer 3 Routing
53-1003627-04