PBR - matching prefix lists

When applying Policy Based Routing (PBR), we use route-maps to match particular traffic. Typically, we use ACLs in the match statements of the route maps, however, we can also use prefix lists.

Which one you will choose depends upon what you want to achieve.

Using access lists gives you more granular control as you can specify specific hosts or ranges of addresses. You can also match source and destination IPv4 and IPv6 addresses as well as Layer 4 protocols (TCP/UDP) and even Layer 4 ports.

Prefix lists are useful when you want to match particular subnets or ranges of subnets. If that is what you want to achieve, then it is preferable.

In general, access lists are used most often with PBR simply because of their granularity. Prefix lists are “more powerful” only in the sense that you can define a whole series of subnets with very concise and efficient statements (rather than just a single range of IP addresses).

Ultimately, what you use comes down to what the policy routing you want to apply requires.




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