OS10 Enterprise Edition User Guide Release 10.4.0E(R3)


Neighbor soft-reconfiguration

BGP soft-reconfiguration allows for fast and easy route changes. Changing routing policies requires a reset of BGP sessions or the TCP connection, for the policies to take effect.

Resets cause undue interruption to traffic due to the hard reset of the BGP cache, and the time it takes to re-establish the session. BGP soft-reconfiguration allows for policies to apply to a session without clearing the BGP session. You can perform a soft-reconfiguration on a per-neighbor basis, either inbound or outbound. BGP soft-reconfiguration clears the policies without resetting the TCP connection. After configuring soft-reconfiguration, use clear ip bgp to make the neighbor use soft reconfiguration.

When you enable soft-reconfiguration for a neighbor and you execute the clear ip bgp soft in command, the update database stored in the router replays and updates are re-evaluated. With this command, the replay and update process triggers only if a route-refresh request is not negotiated with the peer. If the request is negotiated after using the clear ip bgp soft in command, BGP sends a route-refresh request to the neighbor and receives all the peer’s updates.

To use soft reconfiguration, or soft reset without preconfiguration, both BGP peers must support the soft route refresh capability. The soft route refresh advertises in the OPEN message sent when the peers establish a TCP session. To determine whether a BGP router supports this capability, use the show ip bgp neighbors command. If a router supports the route refresh capability, the Received route refresh capability from peer message displays.

  1. Enable soft-reconfiguration for the BGP neighbor and BGP template in ROUTER-BGP mode. BGP stores all the updates that the neighbor receives but does not reset the peer-session. Entering this command starts the storage of updates, which is required to do inbound soft reconfiguration.
    neighbor {
                                           ip-address} soft-reconfiguration inbound
  2. Enter Address Family mode in ROUTER-NEIGHBOR mode.
    address-family {[ipv4 | ipv6] [unicast]}
  3. Configure soft-configuration for the neighbors belonging to the template.
    soft-reconfiguration inbound
  4. Clear all information or only specific details in EXEC mode.
    clear ip bgp {
                                           neighbor-address | * } [soft in]
    • * — Clears all peers.
    • neighbor-address — Clears the neighbor with this IP address.

Soft-reconfiguration of IPv4 neighbor

OS10(conf-router-neighbor)# address-family ipv4 unicast
                                 OS10(conf-router-bgp-neighbor-af)# soft-reconfiguration inbound

Soft-reconfiguration of IPv6 neighbor

OS10(conf-router-neighbor)# address-family ipv6 unicast
                                 OS10(conf-router-bgp-neighbor-af)# soft-reconfiguration inbound

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