Administrator Guide
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 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 Configure 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 configuration of a BGP neighbor, always reset it by entering the clear ip bgp * command in
EXEC Privilege mode.
To view the BGP configuration, 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 first 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