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Chapter 42 Configuring IP Unicast Routing Configuring Protocol-Independent Features
To disable redistribution, use the no form of the commands.
The metrics of one routing protocol do not necessarily translate into the metrics of another. For example,
the RIP metric is a hop count, and the IGRP metric is a combination of five qualities. In these situations,
an artificial metric is assigned to the redistributed route. Uncontrolled exchanging of routing information
between different routing protocols can create routing loops and seriously degrade network operation.
If you have not defined a default redistribution metric that replaces metric conversion, some automatic
metric translations occur between routing protocols:
• RIP can automatically redistribute static routes. It assigns static routes a metric of 1 (directly
connected).
• Any protocol can redistribute other routing protocols if a default mode is in effect.
Configuring Policy-Based Routing
You can use policy-based routing (PBR) to configure a defined policy for traffic flows. By using PBR,
you can have more control over routing by reducing the reliance on routes derived from routing
protocols. PBR can specify and implement routing policies that allow or deny paths based on:
• Identity of a particular end system
• Application
• Protocol
You can use PBR to provide equal-access and source-sensitive routing, routing based on interactive
versus batch traffic, or routing based on dedicated links. For example, you could transfer stock records
to a corporate office on a high-bandwidth, high-cost link for a short time while transmitting routine
application data such as e-mail over a low-bandwidth, low-cost link.
With PBR, you classify traffic using access control lists (ACLs) and then make traffic go through a
different path. PBR is applied to incoming packets. All packets received on an interface with PBR
enabled are passed through route maps. Based on the criteria defined in the route maps, packets are
forwarded (routed) to the appropriate next hop.
• If packets do not match any route map statements, all set clauses are applied.
• If a statement is marked as permit and the packets do not match any route-map statements, the
packets are sent through the normal forwarding channels, and destination-based routing is
performed.
• For PBR, route-map statements marked as deny are not supported.
For more information about configuring route maps, see the “Using Route Maps to Redistribute Routing
Information” section on page 42-93.
You can use standard IP ACLs to specify match criteria for a source address or extended IP ACLs to
specify match criteria based on an application, a protocol type, or an end station. The process proceeds
through the route map until a match is found. If no match is found, normal destination-based routing
occurs. There is an implicit deny at the end of the list of match statements.
Step 7 show route-map Display all route maps configured or only the one
specified to verify configuration.
Step 8 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose