EIGRP Route-Map Filtering

[lagapidis (Lazarus Agapidis)]

Hello Philip

How the route-map is used will make a difference in how it is interpreted as far as the permit and deny statements go. If you look at this post, you will see that when using redistribution, a deny statement in the ACL will not generate a match:

Introduction to Route-maps

Hello Justin A route-map will indeed stop processing route-map statements whenever a match is achieved. Now a route map has a particular behaviour when applied to redistribution. First of all, as stated in this Cisco documentation: If you use an ACL in a route-map permit or deny clause, and the ACL denies a route, then the route-map clause match is not found and the next route-map clause is evaluated. So a match of your permit_L0 ACL will not result in a match for sequence 10 of your rout…

However, when using a distribute-list as is in this case, then the deny statement in the ACL does match the prefix. And it actually plays a role in the outcome of the distribution list.

I labbed it up and found the following:

• ACL deny and route-map deny result in the prefix being blocked
• ACL deny and route-map permit result in the prefix being blocked
• ACL permit and route-map deny result in the prefix being blocked
• ACL permit and route-map permit result in the prefix not being blocked

So for distribute lists, it seems the permit/deny statements must be both permit in order for the prefix to be permitted.

I hope this has been helpful!

Laz