Intel 480T User Manual page 170

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IP Unicast Routing
A static route must be associated with a valid IP subnet. An IP
subnet is associated with a single VLAN by its IP address and
subnet mask. If the VLAN is subsequently deleted, the static route
entries using that subnet must be deleted manually.
Multiple Routes
When there are multiple, conflicting choices of a route to a
particular destination, the router picks the route with the longest
matching network mask. If these are still equal, the router picks the
route using the following criteria (in the order specified):
• Directly attached network interfaces
• ICMP redirects (refer to Table 47, later in this chapter)
• Static routes
• Directly attached network interfaces that are not active.
If you define multiple default routes, the route that has the lowest
metric is used. If there are multiple default routes that have the same
lowest metric, the system picks one of the routes.
You can also configure blackhole routes — traffic to these
destinations is silently dropped.
IP Route Sharing
IP route sharing allows multiple equal-cost routes to be used
concurrently. IP route sharing can be used with static routes or with
OSPF routes. In OSPF, this capability is referred to as equal cost
multi-path (ECMP) routing. To use IP route sharing, use the
following command:
enable route sharing
Next, configure static routes and/or OSPF as you would normally.
As many as five ECMP routes can be used for a given destination.
Route sharing is useful only in instances where you are constrained
for bandwidth. This is typically not the case using 480T switches.
Using route sharing makes router troubleshooting more difficult
because of the complexity in predicting the path over which the
traffic will travel.