MikroTik Certified Network Associate (MTCNA) Modules Practice Test

Firewall Service Ports are used to activate and manage masquerade (NAT) helpers for protocols that open additional data connections on dynamic ports. Some applications, like FTP or SIP, establish a control connection on a well-known port but negotiate data ports separately. The masquerade helper watches those control signals and rewrites the related data port numbers in the return traffic so the translated addresses stay consistent through the NAT. Without these helpers, NAT can break such protocols because the data channel wouldn’t be redirected correctly. So these ports specifically enable the correct handling of those protocols behind a firewall, rather than performing encryption, DNS filtering, or simple logging.