Understanding Route Maps in Cisco IOS: Policy Control in Action

June 2012   |   9 min read

In Cisco IOS, route maps serve as a highly flexible tool for defining conditional routing and policy enforcement. They are widely used in policy-based routing (PBR), redistribution, filtering, and advanced BGP/OSPF manipulations. This post dives into their syntax, structure, and best practices.

What is a Route Map?

A route map is essentially a conditional if-then construct for modifying or filtering routes. Each route map comprises multiple numbered entries called clauses. These are evaluated sequentially until a match occurs, making the order of entries critical.

Route Map Use Cases

• Policy-Based Routing (PBR): Forwarding decisions based on source IP or packet attributes, not just destination.
• Redistribution Control: Manipulating which routes are injected between protocols (e.g., OSPF to BGP).
• Prefix Filtering: Allow or deny based on prefix-lists or access-lists.
• Attribute Manipulation: Changing BGP metrics (MED, weight, local preference).

Route Map Syntax Overview

route-map <name> permit|deny <sequence>
  match ...
  set ...
  

Each clause contains match statements (criteria) and set statements (actions). If no match is made, the next clause is evaluated. If no clauses match, the route is denied by default.

Policy-Based Routing Example

access-list 101 permit ip 192.168.10.0 0.0.0.255 any

route-map PBR permit 10
  match ip address 101
  set ip next-hop 10.1.1.1

interface FastEthernet0/0
  ip policy route-map PBR
  

This configuration routes traffic from 192.168.10.0/24 to next-hop 10.1.1.1 regardless of the routing table.

Controlling Redistribution

Let’s look at filtering route redistribution into OSPF:

route-map REDIST deny 10
  match ip address 10

route-map REDIST permit 20

router ospf 1
  redistribute eigrp 100 route-map REDIST
  

This example denies redistribution of certain prefixes while allowing all others.

Match and Set Commands

Some of the most common match commands:

• match ip address
• match interface
• match metric
• match route-type

Useful set commands include:

• set ip next-hop
• set metric
• set local-preference
• set weight

Best Practices

• Use sequence numbers in increments (e.g., 10, 20, 30) for flexibility.
• Test route-map logic with show route-map and debug ip policy.
• Document the logic inside config with comments.
• Combine with prefix-lists for efficient and readable filtering.

Verifying Route Maps

Verification tools:

• show route-map
• show ip policy
• show ip bgp or ospf database
• debug ip policy (use with care)

Conclusion

Route maps are foundational tools in Cisco IOS. Whether directing traffic with PBR or shaping protocol behavior, mastering route-map logic will elevate your capabilities in enterprise network design and troubleshooting.

Eduardo Wnorowski is a network infrastructure consultant and technologist.
With over 17 years of experience in IT and consulting, he brings deep expertise in networking, security, infrastructure, and transformation.
Connect on Linkedin