A method of processing data packets, the method executable by a router. The method comprises receiving an indication of a UDP port number associated with a port used by a DNS server and a session duration for the port; receiving a UDP packet; in response to a destination port of the UDP packet matching the DNS port number, sending by a NAT component of the router, the UDP packet to an ALG DNS handler of the router. The method further comprises analyzing, by the ALG DNS handler, a payload length of the at least one UDP packet and verifying whether the UDP packet meets a processing condition. The method further comprises determining a DNS packet type.