Di Posting Oleh : Simple Learning
Kategori : BGP Core Technologies Routing
Prerequisites: CCNP level skills.
Topology
Task 1
Solution
Task 1
R5 should filter out all class A prefixes starting with 40.x.x.x. Configure routers in such a way that changing the inbound filtering policy on R5 should force R3 to apply the right filtering preventing it from sending prefixes R5 does not wish to receive.
R3 Configuration:
!
router bgp 123
no synchronization
bgp router-id 172.16.103.3
bgp log-neighbor-changes
network 172.16.103.0 mask 255.255.255.0
neighbor 10.1.13.1 remote-as 123
neighbor 10.1.13.1 route-reflector-client
neighbor 10.1.13.1 next-hop-self
neighbor 10.1.23.2 remote-as 123
neighbor 10.1.23.2 route-reflector-client
neighbor 10.1.23.2 next-hop-self
neighbor 10.1.35.5 remote-as 50
neighbor 10.1.35.5 capability orf prefix-list receive
no auto-summary
no synchronization
bgp router-id 172.16.103.3
bgp log-neighbor-changes
network 172.16.103.0 mask 255.255.255.0
neighbor 10.1.13.1 remote-as 123
neighbor 10.1.13.1 route-reflector-client
neighbor 10.1.13.1 next-hop-self
neighbor 10.1.23.2 remote-as 123
neighbor 10.1.23.2 route-reflector-client
neighbor 10.1.23.2 next-hop-self
neighbor 10.1.35.5 remote-as 50
neighbor 10.1.35.5 capability orf prefix-list receive
no auto-summary
!
R5 Configuration:
!
router bgp 50
no synchronization
bgp router-id 172.16.105.5
bgp log-neighbor-changes
network 172.16.105.0 mask 255.255.255.0
neighbor 10.1.35.3 remote-as 123
neighbor 10.1.35.3 capability orf prefix-list send
no auto-summary
no synchronization
bgp router-id 172.16.105.5
bgp log-neighbor-changes
network 172.16.105.0 mask 255.255.255.0
neighbor 10.1.35.3 remote-as 123
neighbor 10.1.35.3 capability orf prefix-list send
no auto-summary
!
Verification:
Pic. 2 - Outbound Route Filtering Negotiated between R3 and R5.
ORF has been enabled and supports prefix-lists only (as of writing this post). Now, I can apply the prefix-list based filtering as per Task 1.
Pic. 3 - BGP Table on R5 Before Filtering.
R5 Configuration:
!
ip prefix-list FILTER seq 5 deny 40.0.0.0/8 le 32
ip prefix-list FILTER seq 10 permit 0.0.0.0/0 le 32
!
ip prefix-list FILTER seq 5 deny 40.0.0.0/8 le 32
ip prefix-list FILTER seq 10 permit 0.0.0.0/0 le 32
!
router bgp 50
no synchronization
bgp router-id 172.16.105.5
bgp log-neighbor-changes
network 172.16.105.0 mask 255.255.255.0
neighbor 10.1.35.3 remote-as 123
neighbor 10.1.35.3 capability orf prefix-list send
neighbor 10.1.35.3 prefix-list FILTER in
no auto-summary
no synchronization
bgp router-id 172.16.105.5
bgp log-neighbor-changes
network 172.16.105.0 mask 255.255.255.0
neighbor 10.1.35.3 remote-as 123
neighbor 10.1.35.3 capability orf prefix-list send
neighbor 10.1.35.3 prefix-list FILTER in
no auto-summary
!
Verification:
Pic. 4 - Prefix-List Applied on R5.
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