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ip-address— Neighbor’s IP address.
peer-group-name— Name of the peer group. See section 8-19.
version-number— 2, 3, or 4.
Purpose: Currently, the default BGP version number is 4. Cisco’s implementation of BGP begins using version 4 and negotiates down to version 2. If you do not want to form a neighbor connection with a router that is not running version 4, you can lock down the version number using this command.
Cisco IOS Software Release: 10.0. Peer group support was added in Release 11.0.
The following configuration locks down the version number with one neighbor to 4 and leaves the version number in auto-negotiate for the other neighbors:
router bgp 1
neighbor 10.1.1.2 remote-as 2
neighbor 10.1.1.2 version 4
neighbor 10.2.1.2 remote-as 3
neighbor 10.3.1.2 remote-as 4
Verify the version number by using the show ip bgp neighbors command:
rtrA#show ip bgp neighbors
BGP neighbor is 10.1.1.2, remote AS 2, external link
Index 1, Offset 0, Mask 0x2
BGP version 4, remote router ID 10.1.1.2
BGP state = Established, table version = 7, up for 00:53:07
Last read 00:00:08, hold time is 180, keepalive interval is 60 seconds
Minimum time between advertisement runs is 30 seconds
Received 375 messages, 0 notifications, 0 in queue
Sent 343 messages, 0 notifications, 0 in queue
Prefix advertised 0, suppressed 0, withdrawn 0
Connections established 20; dropped 19
Last reset 00:53:28, due to User reset
6 accepted prefixes consume 192 bytes, maximum limit 8
Threshold for warning message 75%
0 history paths consume 0 bytes
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Local host: 10.1.1.1, Local port: 11015
Foreign host: 10.1.1.2, Foreign port: 179
Verify that the BGP neighbors are in the Established state using the show ip bgp neighbors command. If the neighbor relationship is not in the Established state, check for a version number mismatch between neighbors.
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