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Configuring IP Unicast Routing
Configuring Protocol-Independent Features
Configuring the Number of Equal-Cost Routing Paths
When a router has two or more routes to the same network with the same metrics, these routes can be thought of as
having an equal cost. The term parallel path is another way to see occurrences of equal-cost routes in a routing table. If
a router has two or more equal-cost paths to a network, it can use them concurrently. Parallel paths provide redundancy
in case of a circuit failure and also enable a router to load balance packets over the available paths for more efficient use
of available bandwidth.
Although the router automatically learns about and configures equal-cost routes, you can control the maximum number
of parallel paths supported by an IP routing protocol in its routing table.
DETAILED STEPS
Command
1.
configure terminal
2.
router {bgp | rip | ospf | eigrp}
3.
maximum-paths maximum
4.
end
5.
show ip protocols
6.
copy running-config startup-config
Use the no maximum-paths router configuration command to restore the default value.
EXAMPLE
The following example shows how to allow a maximum of 16 paths to a destination in an OSPF routing process:
Switch(config)# router ospf 3
Switch(config-router)# maximum-paths 16
Configuring Static Unicast Routes
Static unicast routes are user-defined routes that cause packets moving between a source and a destination to take a
specified path. Static routes can be important if the router cannot build a route to a particular destination and are useful
for specifying a gateway of last resort to which all unroutable packets are sent.
The switch retains static routes until you remove them. However, you can override static routes with dynamic routing
information by assigning administrative distance values. Each dynamic routing protocol has a default administrative
distance, as listed in Table 2. If you want a static route to be overridden by information from a dynamic routing protocol,
set the administrative distance of the static route higher than that of the dynamic protocol.
Purpose
Enter global configuration mode.
Enter router configuration mode.
Set the maximum number of parallel paths for the protocol
routing table. The range is from 1 to 8; the default is 4 for most
IP routing protocols, but only 1 for BGP.
Return to privileged EXEC mode.
Verify the setting in the Maximum path field.
(Optional) Save your entries in the configuration file.
908
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