I just recently learned that the BGP Soft Reset feature in Cisco IOS is automatically implemented in software release 12.0(2)S and later. Earlier software releases required the neighbor soft-reconfiguration in the BGP configuration to dynamically update BGP route-maps, local preference, etc. Without the neighbor soft-configuration enabled any configuration changes required a hard reset of the BGP peer which would interrupt network traffic. There was a memory penalty paid to having the neighbor soft-reconfiguration enabled since the router would keep a duplicate copy of the BGP route table in memory;
Before the BGP Soft Reset Enhancement feature, a soft reset for inbound routing table updates was performed by entering the neighbor soft-reconfiguration router configuration command. This command was used to configure the local BGP router to store all received (inbound) routing policy updates. However, this method uses too much memory because inbound updates are not modified and is not recommended.
I’m guessing this new feature had a significant impact for anyone taking a full Internet BGP table?
Image Credit: Earth 3D by Jan