BGP - Conditional Route Advertisement

Case -1 ADVRTISE-MAP   with EXIST-MAP 















R1


router bgp 101
 bgp asnotation dot
 bgp log-neighbor-changes
 network 11.11.11.11 mask 255.255.255.255
  neighbor 3.3.3.3 remote-as 101
 neighbor 3.3.3.3 update-source Loopback0
 neighbor 3.3.3.3 route-reflector-client
 neighbor 3.3.3.3 next-hop-self
 neighbor 3.3.3.3 advertise-map ADVERTISE exist-map NON

{ if 69.0.0.0/11 is present in BGP table , we will advertise 11.11.11.11/32 to neighbor, otherwise will drop}

int lo10
ip add 11.11.11.11 255.255.255.255

ip prefix-list ADD seq 5 permit 11.11.11.11/32
!
ip prefix-list NON seq 5 permit 69.0.0.0/11
!
route-map ADVERTISE permit 10
 match ip address prefix-list ADD
!
route-map NON permit 10
 match ip address prefix-list NON

R6

router bgp 1.301
 bgp asnotation dot
 bgp log-neighbor-changes
 network 66.6.6.6 mask 255.255.255.255
 aggregate-address 69.0.0.0 255.224.0.0     {Advertising summary route }

 R1 
 

we can see status is advertise as 69.0.0.0/11 is in bgp table.
 

R1#sh ip bgp nei 3.3.3.3 | in Condition-map

  Condition-map NON, Advertise-map ADVERTISE, status: Advertise

R3

R3#sh ip bgp | in 11

 *>i 11.11.11.11/32   1.1.1.1                  0    100      0 i

 *>i 69.0.0.0/11      1.1.1.1                  0    100      0 1.301 i

 *>i 111.111.111.111/32

Now we are removing aggregate address from R6

R6

R6(config)#router bgp 1.301

R6(config-router)#no  aggregate-address 69.0.0.0 255.224.0.0

R1 

R1#sh ip bgp | in 69

 * i 69.1.1.0/24      6.6.6.6                  0    100      0 1.301 ?

 * i 69.2.1.0/24      6.6.6.6                  0    100      0 1.301 ?

 * i 69.3.1.0/24      6.6.6.6                  0    100      0 1.301 ?

 * i 69.4.1.0/24      6.6.6.6                  0    100      0 1.301 ?

R1#

We can see now it is withdraw status as 69.0.0.0/11 is not present in bgp table.

R1#sh ip bgp nei 3.3.3.3 | in Condition-map

  Condition-map NON, Advertise-map ADVERTISE, status: Withdraw

R3

R3#sh ip bgp | in 11

 *>i 111.111.111.111/32           No BGP prefix  for 69.0.0.0/11 and 11.11.11.11/32

Case 2-ADVRTISE-MAP   with NON-EXIST-MAP 

R1

router bgp 101

 neighbor 3.3.3.3 remote-as 101

 neighbor 3.3.3.3 update-source Loopback0

 neighbor 3.3.3.3 route-reflector-client

 neighbor 3.3.3.3 next-hop-self

 neighbor 3.3.3.3 advertise-map ADVERTISE non-exist-map NON

{ if 69.0.0.0/11 is not present in BGP table , we will advertise 11.11.11.11/32 to neighbor, otherwise will drop}

R1
we can see status is advertise as 69.0.0.0/11 is  not in bgp table.

R1#sh ip bgp nei 3.3.3.3 | in Condition-map

  Condition-map NON, Advertise-map ADVERTISE, status: Advertise

R1#

As we don't have 69.0.0.0/11 in bgp table status is advertise

R1#sh ip bgp | in 69

 * i 69.1.1.0/24      6.6.6.6                  0    100      0 1.301 ?

 * i 69.2.1.0/24      6.6.6.6                  0    100      0 1.301 ?

 * i 69.3.1.0/24      6.6.6.6                  0    100      0 1.301 ?

 * i 69.4.1.0/24      6.6.6.6                  0    100      0 1.301 ?

R1#

R3

 

R3#sh ip bgp | in 11

 *>i 11.11.11.11/32   1.1.1.1                  0    100      0 i 

 *>i 111.111.111.111/32

Now 69.0.0.0/11 will be advertise in R6 so it would be in R1 bgp table

R6
 

R6(config-router)#router bgp 1.301

R6(config-router)#  aggregate-address 69.0.0.0 255.224.0.0

R1
 

R1#sh ip bgp | in 69

 * i 69.0.0.0/11      6.6.6.6                  0    100      0 1.301 i

R1#sh ip bgp nei 3.3.3.3 | in Condition-map

  Condition-map NON, Advertise-map ADVERTISE, status: Withdraw

R3

We can see no 11.11.11.11/32 in bgp table
 

R3#sh ip bgp | in 11

 *>i 69.0.0.0/11      1.1.1.1                  0    100      0 1.301 i

 *>i 111.111.111.111/32

R3#