Clearing a BGP Connection
The clear ip bgp command is used to reset a BGP connection. These BGP connections can be reset based on:
• Neighbor's IP address
• Neighbor's AS number
• Peer group name
© 2002, Cisco Systems, Inc. All rights reserved. Cisco CCIE Prep v1.0—Module 8-34
The clear ip bgp command is used to reset a BGP connection. BGP connections can be reset based on:
■ Neighbor's IP address
■ Neighbor's AS number Peer group name
You must reset your BGP connections when any of the following have been modified or added to:
BGP route map BGP distribute list BGP weight
BGP administrative distance BGP timers BGP access list
To clear or reset all BGP connections on a router, issue the command clear ip bgp *.
The problem with this command is it transitions the BGP peer from established to idle, then rebuilds the relationship along with any new policies. In a production environment, this can cause a significant delay and a long down time for the clients.
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Soft Reconfiguration |
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router# clear ip bgp neighbor-ip-address soft |
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R2# clear ip bgp 172.16.23.3 soft |
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router(config-router)# neighbor {ip-address / peer-group-name} soft-reconfiguration outbound |
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R3(config-router)# neighbor 172.16.23.2 soft-reconfiguration outbound |
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© 2002, Cisco Systems, Inc. All rights reserved. Cisco CCIE Prep v1.0—Module |
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clear ip bgp neighbor-ip-address soft
You can eliminate resetting the BGP connections if you perform a soft reconfiguration. With a soft reconfiguration, you do not reset the connection. Instead, you resend all the routing updates.
R2# clear ip bgp 172.16.23.3 soft
When you issue this command, you must also configure the BGP peer (172.16.23.3 = R3) to allow this soft reconfiguration. To allow R2 to perform a soft reconfiguration on R3, you would issue the following command on R3.
neighbor {ip-address / peer-group-name} soft-reconfiguration outbound
R3(config)# router bgp 100
R3(config-router)# neighbor 172.16.23.2 soft-reconfiguration outbound
Continue reading here: EBGP Multihop
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