Di Posting Oleh : Simple Learning
Kategori : BGP Core Technologies Routing
Prerequisites: CCNP level skills.
Note!
Topology from Lab 118.
Topology
Pic. 2 - Regular Expressions Quick Review.
R4 seems to be advertising prefixes that it does not originate making AS 40 a transit autonomous system. Configure R4 so that it only advertises its own prefixes.
Task 2
On R5 filter out all prefixes originated by AS 40.
Solution
Task 1
R4 seems to be advertising prefixes that it does not originate making AS 40 a transit autonomous system. Configure R4 so that it only advertises its own prefixes.
Pic. 3 - Prefixes Advertised by R4 to R1.
Pic. 4 - Prefixes Advertised by R4 to R2.
Notice!
R4 is advertising prefixes originated by other autonomous systems.
R4 Configuration:
!
ip as-path access-list 1 permit ^$
!
!
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
redistribute connected route-map CONN_TO_BGP
neighbor 10.1.14.1 remote-as 10
neighbor 10.1.14.1 filter-list 1 out
neighbor 10.1.24.2 remote-as 20
neighbor 10.1.24.2 filter-list 1 out
no auto-summary
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
redistribute connected route-map CONN_TO_BGP
neighbor 10.1.14.1 remote-as 10
neighbor 10.1.14.1 filter-list 1 out
neighbor 10.1.24.2 remote-as 20
neighbor 10.1.24.2 filter-list 1 out
no auto-summary
!
Verification:
Pic. 5 - Prefixes Advertised by R4 to R1.
R4 is advertising only its own prefixes now.
Task 2
On R5 filter out all prefixes originated by AS 40.
Pic. 6 - R5 Receives Prefixes Originated by AS 40.
R5 Configuration:
!
ip as-path access-list 1 deny _40$
ip as-path access-list 1 permit .*
!
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 30
neighbor 10.1.35.3 filter-list 1 in
no auto-summary
ip as-path access-list 1 permit .*
!
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 30
neighbor 10.1.35.3 filter-list 1 in
no auto-summary
!
Clear ip bgp * in
Verification:
Pic. 7 - R5's BGP Table.
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