By default, the BGP prefix is advertised even if it's not present in the routing table.
It's related only for param " ipv4-unicast network x.x.x.x/x"
set protocols bgp 65001 address-family ipv4-unicast network 10.55.55.0/24 set protocols bgp 65001 neighbor 10.0.0.2 remote-as '65002'
vyos@zab01:~$ sh ip bgp neighbors 10.0.0.2 advertised-routes Network Next Hop Metric LocPrf Weight Path *> 10.55.55.0/24 0.0.0.0 0 32768 i vyos@zab01:~$ show ip route 10.55.55.0/24 % Network not in table
Frr by default don't check it, but have command "bgp network import-check" to prevent it. Check BGP network route exists in IGP.
zab01# conf t zab01(config)# router bgp 65001 zab01(config-router)# bgp network import-check
We need to add this checker as an option in BGP configuration (vyos CLI).
After option (import-check), the prefix will be advertised only if it present in the routing table.
vyos@zab01:~$ show ip bgp neighbors 10.0.0.2 advertised-routes vyos@zab01:~$