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.
vtysh
```
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:~$
```