CCNP Route : Explain ROUTE maps

Route-maps use the concept of sequence numbers, similar to ACLs.?You can specify the sequence number at the end of the route-map command.?By default, the sequence number will be 10.?This is important to note, because if you do not specify the sequence number, it will overwrite the existing statement for sequence number 10.

The route-map command can either have a?permit?or?deny?clause.?A single route-map can contain multiple route-map commands with an implicit deny at the end.

The permit/deny statements have the following logic when it comes to redistribution:

• Permit?statements cause a route to be allowed if matched by the?match?command.?Otherwise the route remains in the list of routes to be examined by the next statement.
• Deny?statements filter the route if matched by the?match?command.?Otherwise the route remains in the list of routes to be examined by the next statement.
• If you use an ACL for matching:
• Permit:?The routes permitted by the ACL are redistributed.
• Deny:??The routes permitted by the ACL are filtered.
• If the route is denied?by the ACL?then the route-map statement is NOT matched and the route remains in the list of routes to be examined by the next statement.
• You can “permit all” by entering a permit statement without any?match?command.
• If you omit both?match/set?commands and leave the route-map statement “empty” then all routes will be allowed without any modifications.

Each route-map statement has two types of commands:

• match?– selects routes to which the statement should be applied
• set –?modifies information if the route is matched (use in?permit?statements only, since in a deny this is no information to modify).

Question :

Router R1 refers to route-map fred when redistributing from EIGRP into OSPF. The entire route-map is listed next.?Which of the following answers must be true based on the configuration asshown?

route-map fred deny 10

?match ip address one

route-map fred deny 20

match ip address two

route-map fred permit 100

A. The third route map clause will allow any routes not already filtered by the first two clauses.

B. Routes permitted by ACL "two" will be redistributed.

C. Routes denied by ACL "one" will be redistributed.

D. All routes will be filtereD

Answer is A.

So from "Routing TCP/IP" perspective first two statemts of route-map will deny routes in access-lists without needing two look at ACL statemts (deny or permit)