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Configuring BGP
BGP Configuration Examples
IPC-338
Cisco IOS IP Configuration Guide
The following example configuration shows how to conditionally originate a default route (0.0.0.0/0) in
RIP when a prefix 10.1.1.0/24 exists in the routing table:
ip prefix-list cond permit 10.1.1.0/24
!
route-map default-condition permit 10
match ip address prefix-list cond
!
router rip
default-information originate route-map default-condition
The following example shows how to configure BGP to accept routing updates from 192.1.1.1 only,
besides filtering on the prefix length:
router bgp
distribute-list prefix max24 gateway allowlist in
!
ip prefix-list allowlist seq 5 permit 192.1.1.1/32
!
The following example shows how to direct the BGP process to filter incoming updates to the prefix
using name1, and match the gateway (next hop) of the prefix being updated to the prefix list name2, on
the Ethernet interface 0:
router bgp 103
distribute-list prefix name1 gateway name2 in ethernet 0.
Route Filtering Configuration Example Specifying a Group of Prefixes
The following example shows how to configure BGP to permit routes with a prefix length up to 24 in
network 192/8:
ip prefix-list abc permit 192.0.0.0/8 le 24
The following example shows how to configure BGP to deny routes with a prefix length greater than in
25 in 192/8:
ip prefix-list abc deny 192.0.0.0/8 ge 25
The following example shows how to configure BGP to permit routes with a prefix length greater than
8 and less than 24 in all address space:
ip prefix-list abc permit 0.0.0.0/0 ge 8 le 24
The following example shows how to configure BGP to deny routes with a prefix length greater than 25
in all address space:
ip prefix-list abc deny 0.0.0.0/0 ge 25
The following example shows how to configure BGP to deny all routes in 10/8, because any route in the
Class A network 10.0.0.0/8 is denied if its mask is less than or equal to 32 bits:
ip prefix-list abc deny 10.0.0.0/8 le 32
The following example shows how to configure BGP to deny routes with a mask greater than 25 in
204.70.1/24:
ip prefix-list abc deny 204.70.1.0/24 ge 25
The following example shows how to configure BGP to permit all routes:
ip prefix-list abc permit 0.0.0.0/0 le 32