Concept Guide

below conguration example, no address family is congured. So, the routing information for the IPv4 unicast address family is advertised
by default.
1 Assign an AS number and enter ROUTER BGP mode.
CONFIGURATION mode
router bgp as-number
• as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte) or 0.1 to 65535.65535 (Dotted format).
Only one AS is supported per system.
NOTE: If you enter a 4-Byte AS number, 4-Byte AS support is enabled automatically.
2 Enable 4-Byte support for the BGP process.
CONFIG-ROUTER-BGP mode
bgp four-octet-as-support
NOTE: This command is OPTIONAL. Use it only if you support 4-Byte AS numbers or if you support AS4 number
representation. Disable 4-Byte support and return to the default 2-Byte format by using the no bgp four-octet-as-
support command. You cannot disable 4-Byte support if you currently have a 4-Byte ASN congured.
3
Add a neighbor as a remote AS.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group name} remote-as as-number
• ip-address: IP address of the neighbor
• peer-group name: 16 characters
• as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte) or 0.1 to 65535.65535 (Dotted format)
NOTE
: Neighbors that are dened using the neighbor remote-as command in the CONFIGURATION-ROUTER-BGP
mode exchange IPv4 unicast address prexes only. To exchange other address prexes (IPv6/IPv4 multicast), the
neighbors must be activated using neighbor activate command under the respective address family conguration such
as
address-family ipv6 unicast (for IPv6) and address-family ipv4 multicast (for IPv4 multicast).
You must Congure Peer Groups before assigning it a remote AS.
4 Enable the BGP neighbor.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6–address | peer-group-name} no shutdown
5 Specify a network to this AS and add the routing information to the BGP routing table.
CONFIG-ROUTER-BGP mode
network ip-address mask
You can provide the mask IP address in slash format too. Eg. 10.10.21.0/24
6 Congure a xed 32–bit router ID for the local device running BGP.
CONFIG-ROUTER-BGP mode
bgp router-id ip-address
Example conguration steps to enable BGP, congure BGP router-id and network
NOTE
: When you change the conguration of a BGP neighbor, always reset it by entering the clear ip bgp * command in
EXEC Privilege mode.
188 Border Gateway Protocol (BGP)