ORF short notes

Hello

ORF is a method of limiting routing updates sent from router B to router A by creating a prefix-list on router A and sending it over to router B so that router B applies it outbound towards router A. Why? it is always better to limit routing updates outbound than inbound on the other end because this saves bandwidth.

  1. enable capability on router B
    ROUTER B: neighbor 1.1.1.1 capability orf prefix-list both
  2. create a loopback on router B and advertise it into BGP

int loop22

ip addr 22.22.22.22 255.255.255.255

router bgp 100

network 22.22.22.22 mask 255.255.255.255

3. Enable capability on router A

 

ROUTER A: neighbor 2.2.2.2 capability orf prefix-list both

4. Create a prefix list that denies some prefix and apply it INBOUND (yes, inbound!) towards router B

neighbor 2.2.2.2 prefix-list dontsendloopback22 in

ip prefix-list dontsendloopback22 deny 22.22.22.22/32

ip prefix-list dontsendloopback22 permit 0.0.0.0/0 le 32

5. Soft clear BGP for the prefix filter.

clear ip bgp 2.2.2.2 soft in prefix-filter

6. Watch the filter being applied on router B:

RouterB#show ip bgp neighbors 1.1.1.1 received prefix-filter
Address family: IPv4 Unicast
ip prefix-list 1.1.1.1: 2 entries
seq 5 deny 22.22.22.22/32
seq 10 permit 0.0.0.0/0 le 32

 

Skomentuj

Wprowadź swoje dane lub kliknij jedną z tych ikon, aby się zalogować:

Logo WordPress.com

Komentujesz korzystając z konta WordPress.com. Wyloguj /  Zmień )

Zdjęcie na Google

Komentujesz korzystając z konta Google. Wyloguj /  Zmień )

Zdjęcie z Twittera

Komentujesz korzystając z konta Twitter. Wyloguj /  Zmień )

Zdjęcie na Facebooku

Komentujesz korzystając z konta Facebook. Wyloguj /  Zmień )

Połączenie z %s