Administrator Guide

NOTE: Use it only if you support 4-Byte AS numbers or if you support AS4 number representation. If you are
supporting 4-Byte ASNs, enable this command.
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.
Disabling 4-Byte AS numbers also disables ASDOT and ASDOT+ number representation. All AS numbers are displayed in
ASPLAIN format.
b Enable IPv4 multicast or IPv6 mode.
CONFIG-ROUTER-BGP mode
address-family [ipv4 | ipv6} vrf
Use this command to enter BGP for IPv6 mode (CONF-ROUTER_BGPv6_AF).
2 Add a neighbor as a remote AS.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group name} remote-as as-number
• 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)
Formats: IP Address A.B.C.D
You must Congure Peer Groups before assigning it a remote AS.
3 Enable the BGP neighbor.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group-name} no shutdown
Examples of the show ip bgp Commands
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.
To view the BGP conguration, enter show config in CONFIGURATION ROUTER BGP mode. To view the BGP status, use the show
ip bgp summary command in EXEC Privilege mode. The rst example shows the summary with a 2-byte AS number displayed (in bold);
the second example shows that the summary with a 4-byte AS number using the
show ip bgp summary command (displays a 4–byte
AS number in bold).
The following example shows the show ip bgp summary command output (2–byte AS number displays).
R2#show ip bgp summary
BGP router identifier 192.168.10.2, local AS number 65123
BGP table version is 1, main routing table version 1
1 network entrie(s) using 132 bytes of memory
1 paths using 72 bytes of memory
BGP-RIB over all using 73 bytes of memory
1 BGP path attribute entrie(s) using 72 bytes of memory
1 BGP AS-PATH entrie(s) using 47 bytes of memory
5 neighbor(s) using 23520 bytes of memory
Neighbor AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/Pfx
10.10.21.1 65123 0 0 0 0 0 never Active
10.10.32.3 65123 0 0 0 0 0 never Active
100.10.92.9 65192 0 0 0 0 0 never Active
192.168.10.1 65123 0 0 0 0 0 never Active
192.168.12.2 65123 0 0 0 0 0 never Active
R2#
Border Gateway Protocol IPv4 (BGPv4)
189