Route-maps with continue clauses

Hello

Today let’s have a brief look at what we can use the continue keyword for in BGP route-maps.

Let’s say we have four customers: three customers in AS100 and one customer in AS200. We need to send routes from the customers in AS100 to other ISPs, but not the routes from the customer in AS200.

On our edge, we gave each customer a community:

Customer A: 100:10 (Acomm)

Customer B: 200:20 (Bcomm)

Customer C: 300:30 (Ccomm)
Now we want to advertise these routes to some other ISPs such that all ISPs get these routes with MED equal 100, but AS path prepending will be different. It’s a silly requirement but i only want to demonstrate how the continue phrase can simplify an otherwise complex route-map.

 

A route-map with continue:

 

Route-map X permit 10

match as-path 100

continue

set metric 100

 

Route-map X permit 20

match community Acomm

set as-path prepend 100 100 100

 

Route-map X permit 30

match community Bcomm

set as-path prepend 100 100 100 100

 

Route-map X permit 40

match community Ccomm

set as-path prepend 100 100 100 100 100

 

 

———————–Route-map without continue—

Route-map X permit 20

match as-path 100

match community Acomm

set as-path prepend 100 100 100

set metric 100

 

Route-map X permit 30

match as-path 100

match community Bcomm

set as-path prepend 100 100 100 100

set metric 100

 

Route-map X permit 40

match as-path 100

match community Ccomm

set as-path prepend 100 100 100 100 100

set metric 100