4-Octet ASN Capability Enabled on R1 and Disabled on R2
In the following two examples, 4-Octet ASN capability is enabled on BGP speaker R1 and disabled on R2.
Topology
Figure 1-22: 4-Octet ASN on One Router
R1
#configure terminal | Enter configure mode. |
(config)#bgp extended-asn-cap | Enable 4-octet ASN capability. |
(config)#router bgp 70000 | Assign the ASN value (70000) to the router. |
(config-router)#neighbor 172.20.30.20 remote-as 800 | Specify the neighbor's IP address (172.20.30.20) and the ASN value of the neighbor (800). |
(config-router)# address-family ipv4 unicast | Enter address-family ipv4 unicast mode |
(config-router-af)# neighbor 172.20.30.20 activate | Activate neighbor under address family mode |
(config-router-af)# exit-address-family | Exit address family mode |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
R2
#configure terminal | Enter configure mode. |
(config)#no bgp extended-asn-cap | Disable 4-octet ASN capability. |
(config)#router bgp 800 | Assign the ASN value (800) to the router. |
(config-router)#neighbor 172.20.30.10 remote-as 70000 | Specify the neighbor's IP address (172.20.30.10) and the ASN value of the neighbor (70000). |
(config-router)# address-family ipv4 unicast | Enter address-family ipv4 unicast mode |
(config-router-af)# neighbor 172.20.30.10 activate | Activate neighbor under address family mode |
(config-router-af)# exit-address-family | Exit address family mode |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
Topology
Figure 1-23: 4-Octet ASN
R1
#configure terminal | Enter configure mode. |
(config)#bgp extended-asn-cap | Enable 4-octet ASN capability. |
(config)#router bgp 700 | Assign the ASN value (700) to the router. |
(config-router)#neighbor 172.20.30.20 remote-as 800 | Specify the neighbor's IP address (172.20.30.20) and the ASN value of the neighbor (800). |
(config-router)# address-family ipv4 unicast | Enter address-family ipv4 unicast mode |
(config-router-af)# neighbor 172.20.30.20 activate | Activate neighbor under address family mode |
(config-router-af)# exit-address-family | Exit address family mode |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
R2
#configure terminal | Enter configure mode. |
(config)#no bgp extended-asn-cap | Disable 4-octet ASN capability. |
(config)#router bgp 800 | Assign the ASN value (800) to the router. |
(config-router)#neighbor 172.20.30.10 remote-as 700 | Specify the neighbor's IP address (172.20.30.10) and the ASN value of the neighbor (700). |
(config-router)# address-family ipv4 unicast | Enter address-family ipv4 unicast mode |
(config-router-af)# neighbor 172.20.30.10 activate | Activate neighbor under address family mode |
(config-router-af)# exit-address-family | Exit address family mode |
(config-router)#commit | Commit the candidate configuration to the running configuration. |
Validation
#show ip bgp summary
BGP router identifier 192.168.52.2, local AS number 400000
BGP table version is 1
0 BGP AS-PATH entries
0 BGP community entries
Neighbor V AS MsgRcv MsgSen TblVer InQ OutQ Up/Down State/PfxRcd
10.20.30.2 4 7000 2 3 1 0 0 00:00:08 0
Total number of neighbors 1
Total number of Established sessions 1
#show ip bgp neighbors
BGP neighbor is 10.20.30.1, remote AS 400000, local AS 7000, external link
BGP version 4, local router ID 192.168.52.3, remote router ID 192.168.52.2
BGP state = Established, up for 00:02:20
Last read 00:00:20, hold time is 90, keepalive interval is 30 seconds
Neighbor capabilities:
Route refresh: advertised and received (old and new)
4-Octet ASN Capability: advertised and received
Address family IPv4 Unicast: advertised and received
Received 6 messages, 0 notifications, 0 in queue
Sent 6 messages, 0 notifications, 0 in queue
Route refresh request: received 0, sent 0
Minimum time between advertisement runs is 30 seconds
For address family: IPv4 Unicast
BGP table version 1, neighbor version 1
Index 1, Offset 0, Mask 0x2
Community attribute sent to this neighbor (both)
0 accepted prefixes
0 announced prefixes
Connections established 1; dropped 0
Local host: 10.20.30.2, Local port: 49434
Foreign host: 10.20.30.1, Foreign port: 179
Nexthop: 10.20.30.2
Nexthop global: ::
Nexthop local: ::
BGP connection: non shared network
Last modified date: 10/16/2023