I used ulnerability scanner to scan virtual server IP to found any open port (I have VIP port 443, 22, 80)
result is scanner found UDP port 161 is opened but there is no vip udp port 161 in configuration.
Why is UDP port 161 is found? is it by default that every virtual server is open/received port udp 161 too?
are you sure 161/UDP was detected on the IP address of a virtual server? The BIG-IP will not answer on port 161/UPD as long as there is not a listener defined.
What I think is more likely, is that it was detected on a self IP address. Take a look at K17333, this will explain why a self IP address might be listening on 161/UDP.