Technical Tip : BGP Routing process when 'Soft Reconfiguration' is enabled

[darisandy]

Description	This article describes how FortiGate processes BGP Updates when Soft Reconfiguration is enabled towards that BGP Neighbor.
Scope	FortiGate.
Solution	The picture illustrates how FortiGate processes BGP updates and the related CLI commands for checking prefix status. By understanding this cycle, it is possible to troubleshoot the BGP Routing issue depending on the position where the issue occurred. Whether it is before or after the incoming filter, or if the issue is after the outbound filter. When it is configured, BGP neighborship can be flushed without terminating the BGP session. This is usually needed whenever changes have been made to route filtering. execute router clear bgp ip <neighbor IP> soft Note: If soft reconfiguration is not enabled, the following error will appear when checking received routes: IPv4: FGT # get router info bgp neighbors 192.168.x.x received-routes Inbound soft reconfiguration not enabled No prefix for neighbor 192.168.x.x To fix this issue, enable soft reconfiguration for the IPv4 neighbor: config router bgp     config neighbor         edit "192.168.x.x"             set soft-reconfiguration enable   <-----             set remote-as 65001         next     end end IPv6: FGT # get router info6 bgp neighbors fd12:3456:789a:1::1 received-routes % Inbound soft reconfiguration not enabled % No prefix for neighbor fd12:3456:789a:1::1 To fix this issue, enable soft reconfiguration for the IPv6 neighbor: config router bgp     config neighbor         edit "fd12:3456:789a:1::1"             set soft-reconfiguration6 enable   <-----             set remote-as 65001         next     end end