The prefix "x.x.x.x/28" missing from the output of show bgp neighbors vrf all <neighbor_ip> advertised-routes.

The prefix "x.x.x.x/28" is present in the RIB as a connected route:

mist@node0...> show rib | grep x.x.x.x
... x.x.x.x/28     connected   true ...

The issue stems from the connected route redistribution policy being too restrictive.

The existing configuration for the match-redistributed-connected-routes prefix filter only permits the redistribution of the y.y.y.y.y/28 prefix into BGP:

config authority routing filter match-redistributed-connected-routes rule r0 prefix  y.y.y.y/28

Because the connected route "x.x.x.x/28" is not explicitly included in this prefix filter, it is blocked from being redistributed and subsequently advertised via BGP, despite the general BGP export policy being configured to accept it.

The most direct solution is to add the missing prefix "x.x.x.x/28" to the existing match-redistributed-connected-routes prefix filter.

e.g. below

config authority routing filter match-redistributed-connected-routes type prefix-filter
config authority routing filter match-redistributed-connected-routes name match-redistributed-connected-routes
config authority routing filter match-redistributed-connected-routes rule r1 name r1
config authority routing filter match-redistributed-connected-routes rule r1 prefix x.x.x.x/28