Soft Reconfiguration and Route Refresh in BGP

Soft Reconfiguration

• Description: Soft Reconfiguration is an original non-disruptive method to refresh the BGP Adj-RIBs-In/Out. It serves as an alternative to a "hard reset" of the BGP peering session, allowing you to update the routing information without disrupting the connection.
• Resource Cost: There is an appreciable resource cost associated (consumes a noticeable amount of resources, such as memory and processing power) with Soft Reconfiguration, primarily for Adj-RIBs-In.
  • The resource cost is view and router resource-dependent.
  • It involves maintaining a copy of all received routes on a per-neighbor basis.
• Configuration: Soft Reconfiguration is enabled using the command neighbor x.x.x.x soft-reconfiguration inbound. This command instructs BGP to store a copy of the received routes without requiring a hard reset.

Route Refresh

• Description: Route Refresh is a mechanism defined in RFC 2918, which was first introduced in Cisco IOS 12.2(6)T. It provides a non-disruptive method to refresh both inbound and outbound BGP information at little or no cost.
• Resource Efficiency: Route Refresh is a more efficient and resource-friendly method compared to Soft Reconfiguration.
• Communication: Route Refresh is communicated between BGP peers in the OPEN message capabilities.
• Advantages: This method allows BGP peers to request and refresh the BGP routing information without the resource-intensive storage of Soft Reconfiguration.

Using Soft Reconfiguration or Route Refresh can be important tools for maintaining BGP routing information without requiring a full session reset. However, Route Refresh is generally preferred for its resource efficiency and non-disruptive nature.