BGP community : no-advertise

Trivia : Today i am getting sleep early than usual days, again i will have to wake-up as early as 3.00 AM tomorrow to finish some official work. Before i hibernate let me post a quick lab i had finished today.

Note:
NO-ADVERTISE tells a BGP-speaking router not to send the tagged prefix to any other neighbor, including other iBGP routers.



Basic BGP configurations as per diagram:

Task 1: Advertise the following class B loopback on R4, do not use network statement.

Loopback3 40.0.0.1
Loopback4 40.1.0.1
Loopback5 40.2.0.1
Loopback6 40.3.0.1
Loopback7 44.4.0.1
Loopback8 44.4.32.1
Loopback9 44.4.64.1
Loopback10 44.4.96.1

Task 2: On R4 advertise the network 40.1.0.0/16 in such a way that R1 and R2 should not advertise 40.1.0.0/16 to its EBGP peers.


Solution: Task 1
Since we cant use network statement, we will use redistribute command to advertise the loopbacks

ip prefix-list NET_40 seq 10 permit 40.0.0.0/8 le 16
!
ip prefix-list NET_44 seq 10 permit 44.4.0.0/16 le 19

route-map ADV_LOOP permit 10
match ip address prefix-list NET_40
!
route-map ADV_LOOP permit 20
match ip address prefix-list NET_44




Verify the network on R1 and R2



Also verify that 40.1.0.0/16 is received on R3 as well.



Solution : Task 2 (use community - no-advertise)

ip prefix-list NO_ADV seq 5 permit 40.1.0.0/16
!
route-map NO_ADV permit 5
match ip address prefix-list NO_ADV
set community no-advertise
!
route-map NO_ADV permit 10




verify the BGP table on R1, it says that the route




Lets verify the BGP table of R3 again.




Mission accomplished. Over to bed!