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Border Gateway Protocol IPv4 (BGPv4) | 227
Use these commands in the following sequence, starting in the CONFIGURATION mode to establish BGP
sessions on the router.
Step Command Syntax Command Mode Purpose
1
router bgp as-number CONFIGURATION Assign an AS number and enter the
ROUTER BGP mode.
AS Number: 0-65535 (2-Byte) or
1-4294967295 (4-Byte) or 0.1-65535.65535
(Dotted format)
Only one AS is supported per system
If you enter a 4-Byte AS Number, 4-Byte AS Support is enabled
automatically.
1a bgp four-octet-as-support CONFIG-ROUTER-B
GP
Enable 4-Byte support for the BGP process.
Note: This is an OPTIONAL command.
Enable if you want to use 4-Byte AS
numbers or if you support AS4 Number
Representation.
Use it only if you support 4-Byte AS Numbers or if you support AS4
Number Representation. If you are supporting 4-Byte ASNs, this
command must be enabled first.
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 configured.
Disabling 4-Byte AS Numbers also disables ASDOT and ASDOT+
number representation. All AS Numbers will be displayed in
ASPLAIN format.
1b address-family [ipv4 | ipv6} CONFIG-ROUTER-B
GP
Enable IPv4 multicast or IPv6 mode.
Use this command to enter BGP for IPv6
mode (CONF-ROUTER_BGPv6_AF).
2
neighbor {ip-address | peer-group
name
} remote-as as-number
CONFIG-ROUTER-B
GP
Add a neighbor as a remote AS.
Formats:
IP Address A.B.C.D
Peer-Group Name: 16 characters
AS-number: 0-65535 (2-Byte) or
1-4294967295 (4-Byte) or 0.1-65535.65535
(Dotted format)
You must Configure Peer Groups before assigning it a remote AS.
3
neighbor {ip-address |
peer-group-name} no shutdown
CONFIG-ROUTER-B
GP
Enable the BGP neighbor.
Note: When you change the configuration of a BGP neighbor, always reset it by entering the clear
ip bgp
command in EXEC Privilege mode.