Configuring BGP Soft Resetting

BGP soft resetting can refresh the BGP routing table and apply the new policy without closing the BGP connection.

Context

After changing BGP route selection principles, you must reset the BGP connection to validate the new configuration. The BGP connection is thus interrupted.

BGP supports the Route-Refresh capability. When the principles are changed, the system refreshes the BGP routing table automatically. So, BGP connections are not interrupted.

If the neighbor supports the Route-Refresh capability, you can run the refresh bgp command on the local router to manually perform soft resetting for the BGP connection. The routing table of the local router is thus refreshed.

If the neighbor does not support the Route-Refresh capability, you can run the peer keep-all-routes command on the local router. In this manner, the BGP routing table of the local router can be refreshed.

Procedure

Enable the Route-Refresh capability.
1. Access the system view.
  system-view
2. Access the BGP view.
  bgp { as-number-plain | as-number-dot }
3. Enable the Route-Refresh capability.
  peer { ipv4-address | group-name } capability-advertise route-refresh
  
  If the Route-Refresh capability is enabled on all BGP routers, the local router advertises Route-Refresh messages to its peer if the BGP routing policy changes. Upon receiving this message, the peer sends the message to the local router again. In this case, the BGP routing table is dynamically refreshed and the new policy is applied without interrupting BGP connections.
4. Return to the system view.
  quit
5. Return to the user view.
  quit
6. Configure BGP soft reset.
  refresh bgp [ vpn-instance vpn-instance-name ipv4-family | vpnv4 | vpn-target ] { all | ipv4-address | group group-name | external | internal } { export | import }
Keep all the routing updates of the peers.
1. Access the system view.
  system-view
2. Access the BGP view.
  bgp { as-number-plain | as-number-dot }
3. Access the BGP IPv4 unicast address family view.
  ipv4-family unicast
4. Keep all the routing updates of the peer.
  peer { ipv4-address | group-name } keep-all-routes
  
  After this command is used, all routing updates of the specified peer are kept regardless of whether the filtering policy is used. When BGP connections are soft reset, this information can be used to generate BGP routes.
  
  This command must be run on the local device and its peers. If the peer keep-all-routes command is run on the device for the first time, the sessions between the device and its peers are reestablished.
  
  The peer keep-all-routes command does not need to be run on the router that supports route-refresh. If the peer keep-all-routes command is run on the router, the sessions between the router and its peers will not be reestablished but the refresh bgp command does not take effect on the router.