Prerequisites: CCNP level skills.
Note!
Topology from Lab 118.
Topology
Task 1
On R4 advertise into BGP two summary prefixes representing subnets 40.x.x.x/16 and 44.4.x.x/19.
Task 2
Configure R2 in such a way that apart from the two aggregates it BGP table also injects 40.2.0.0/16.
Solution
Task 1
On R4 advertise into BGP two summary prefixes representing subnets 40.x.x.x/16 and 44.4.x.x/19.
R4 Configuration:
!
router bgp 40
no synchronization
bgp router-id 172.16.104.4
bgp log-neighbor-changes
network 172.16.104.0 mask 255.255.255.0
network 172.16.144.0 mask 255.255.255.0
aggregate-address 44.4.0.0 255.255.128.0 summary-only
aggregate-address 40.0.0.0 255.252.0.0 summary-only
redistribute connected route-map CONN_TO_BGP
neighbor 10.1.14.1 remote-as 10
neighbor 10.1.24.2 remote-as 20
no auto-summary
router bgp 40
no synchronization
bgp router-id 172.16.104.4
bgp log-neighbor-changes
network 172.16.104.0 mask 255.255.255.0
network 172.16.144.0 mask 255.255.255.0
aggregate-address 44.4.0.0 255.255.128.0 summary-only
aggregate-address 40.0.0.0 255.252.0.0 summary-only
redistribute connected route-map CONN_TO_BGP
neighbor 10.1.14.1 remote-as 10
neighbor 10.1.24.2 remote-as 20
no auto-summary
!
Verification:
Pic. 2 - R2's BGP table (aggregates).
Task 2
Configure R2 in such a way that apart from the two aggregates it BGP table also injects 40.2.0.0/16.
R2 Configuration:
!
ip prefix-list ADV_ROUTER seq 5 permit 10.1.24.4/32
!
ip prefix-list EXIST seq 5 permit 40.0.0.0/14
!
ip prefix-list INJECT_PFX seq 5 permit 40.2.0.0/16
!
route-map TO_BE_INJECTED permit 10
set ip address prefix-list INJECT_PFX
!
route-map MUST_EXIST permit 10
match ip address prefix-list EXIST
match ip route-source prefix-list ADV_ROUTER
!
router bgp 20
no synchronization
bgp router-id 172.16.102.2
bgp log-neighbor-changes
bgp inject-map TO_BE_INJECTED exist-map MUST_EXIST
network 172.16.102.0 mask 255.255.255.0
neighbor 10.1.23.3 remote-as 30
neighbor 10.1.24.4 remote-as 40
no auto-summary
!
!
ip prefix-list EXIST seq 5 permit 40.0.0.0/14
!
ip prefix-list INJECT_PFX seq 5 permit 40.2.0.0/16
!
route-map TO_BE_INJECTED permit 10
set ip address prefix-list INJECT_PFX
!
route-map MUST_EXIST permit 10
match ip address prefix-list EXIST
match ip route-source prefix-list ADV_ROUTER
!
router bgp 20
no synchronization
bgp router-id 172.16.102.2
bgp log-neighbor-changes
bgp inject-map TO_BE_INJECTED exist-map MUST_EXIST
network 172.16.102.0 mask 255.255.255.0
neighbor 10.1.23.3 remote-as 30
neighbor 10.1.24.4 remote-as 40
no auto-summary
!
Verification:
Pic. 3 - R2 Injects the Prefix into BGP.
After around a minute, the prefix gets injected. The route-map which specifies the condition for the prefix injection (here: EXIST) must refer to the advertising router's address. Otherwise the conditional route injections does not seem to work.
