Enable BGP4 Cooperative Route Filtering

Cooperative filtering conserves resources by eliminating unnecessary route updates and filter processing.

Access global configuration mode.
```
device# configure terminal
```
Configure the IP prefix list instance.
```
device(config)# ip prefix-list Routesfrom1234 deny 10.20.0.0/24
device(config)# ip prefix-list Routesfrom1234 permit 10.0.0.0/0 le 32
```
The first example denies the routes in the Routesfrom1234 prefix list for the specified IP prefix and prefix length. The second example permits the routes in the Routesfrom1234 prefix list for the specified IP prefix and prefix length, where the subnet mask length must be less than or equal to 32.
Access BGP configuration mode.
```
device(config)# router bgp
```

Access IPv4 address family configuration mode.

device(config-bgp-router)# address-family ipv4 unicast

Filter the incoming route updates from the specified BGP neighbor.
```
device(config-bgp-ipv4u)# neighbor 10.2.3.4 prefix-list Routesfrom1234 in
```
This example specifies the neighbor prefix-list command, the IPv4 address of the neighbor, the prefix list named Routesfrom1234, and the keyword in.
Advertise ORF send capabilities.
```
device(config-bgp-ipv4u)# neighbor 10.2.3.4 capability orf prefixlist send
```
This example specifies the neighbor capability orf prefixlist command with the send keyword.

The following example summarizes the commands in this procedure.

device# configure terminal
device(config)# ip prefix-list Routesfrom1234 deny 10.20.0.0/24
device(config)# ip prefix-list Routesfrom1234 permit 10.0.0.0/0 le 32
device(config)# router bgp
device(config-bgp-router)# address-family ipv4 unicast
device(config-bgp-ipv4u)# neighbor 10.2.3.4 prefix-list Routesfrom1234 in
device(config-bgp-ipv4u)# neighbor 10.2.3.4 capability orf prefixlist send