Troubleshooting Tip: BGP debug log message 'denied due to filter'

Assume the following scenario:

HUB ---------------SPOKE.

On the HUB side, see for the specific network route advertised and the Spoke side also received the route but still not installed in the routing table.

Starting from v7.2.0+, it is possible to collect BGP debugs for a specific neighbor by using the filter command

'diag ip router bgp set-filter neighbor <neighbor address>'.

Follow this KB article for more details: Technical Tip: Capture BGP debugs for a specific neighbor.

To verify the BGP debug command:

diagnose ip router bgp all di
diagnose ip router bgp updates en
diagnose ip router bgp level info
diagnose debug enable

execute router clear bgp ip <neighbour ip> soft  

Run for 3 minutes after disabling with the below command:

diagnose debug reset

The below logs on denied due to filter:

2024-12-06 13:26:34 BGP: 10.100.100.1-Outgoing [RIB] Update: Prefix 10.148.148.0/22 path_id 1 denied due to filter

Configuration:

config router prefix-list
    edit "PL_Receive_Routes"
        config rule
            edit 1
                set action deny
                set prefix 10.148.148.0 255.255.252.0 <----- Due to denied.
                unset ge
                set le 32
            next
            edit 2
                set prefix any
                unset ge
                unset le
            next
        end
    next
end

config router route-map
    edit "RM_Receive_Routes"
        config rule
            edit 1
                set match-ip-address "PL_Receive_Routes"
            next
        end
    next
end