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3. Examples of BGP Route Filtering by Neighbor
The following is an example of BGP path filtering by neighbor. The routes that pass as-path access list
1 will get weight 100. Only the routes that pass as-path access list 2 will be sent to 193.1.12.10.
Similarly, only routes passing access list 3 will be accepted from 193.1.12.10.:
router bgp 200
neighbor 193.1.12.10 remote-as 100
neighbor 193.1.12.10 filter-list test1 weight 100
neighbor 193.1.12.10 filter-list test2 out
neighbor 193.1.12.10 filter-list test3 in
ip aspath-list test1 permit _109_
ip aspath-list test2 permit _200$
ip aspath-list test2 permit ^100$
ip aspath-list test3 deny _690$
ip aspath-list test3 permit .*
4. BGP Route Filtering base on Port Example
The following is an example of BGP path filtering by neighbor. The routes from port e1/O will be filtered
by access list ac1.
router bgp 122
filter e1/0 in access-list acl
Following example filters routes from port s1/0 through using access list filter-network to filter network
number as well as using access list filter-gateway to filter gateway address:
router bgp 100
filter s1/0 in access-list filter-network gateway filter-gateway
Following example filters routes from all ports through using prefix list filter-prefix to filter network
number as well as using access list filter-gateway to filter gateway address:
router bgp 100
filter * in prefix-list filter-prefix gateway filter-gateway
5. Examples of Route Filtering through Prefix List
Following example denies default route 0.0.0.0/0:
ip prefix-list abc deny 0.0.0.0/0
Following example allows routes matching prefix 35.0.0.0/8
ip prefix-list abc permit 35.0.0.0/8
In following example BGP process will only accept prefix length from /8 to /24:
router bgp
network 101.20.20.0
filter * in prefix max24
!
ip prefix-list max24 seq 5 permit 0.0.0.0/0 ge 8 le 24
!
In following configuration, router will filter routes from all ports except of route whose prefix is in the
range of 8-24:
router bgp 12
filter * in prefix-list max24
！
ip prefix-list max24 seq 5 permit 0.0.0.0/0 ge 8 le 24
The following are examples of other prefix list configurations.
Following example allows route whose prefix length not larger than 24 in net 192/8:
ip prefix-list abc permit 192.0.0.0/8 le 24
Model Name
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