Border Gateway Protocol (BGP) soft reconfiguration can be performed by issuing the clear ip bgp command. The clear ip bgp command rebuilds the BGP routing table. This command can be used to begin a soft or hard reset. A soft reset uses stored prefix information in order to rebuild the BGP routing tables without breaking down any active peering sessions, whereas a hard reset breaks down the active peering sessions and then rebuilds the BGP routing tables. Typically, the clear ip bgp * soft command initiates soft reconfiguration; however, if all BGP routers support soft reconfiguration, the soft keyword is assumed by default.
BGP soft reconfiguration does not require any configuration to support outbound updates, because outbound updates are stored automatically. However, soft reconfiguration requires that you issue the neighbor rneighbor-id soft-reconfiguration inbound command before it stores inbound updates from a neighbor. These updates are stored in memory, so soft reconfiguration is very memory intensive. When soft reconfiguration inbound is configured, the route will display (received only) in the output of the show ip bgp command.