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Prestige 2002 Series User’s Guide
44 Chapter 5 Introduction to VoIP
Figure 16 Full Cone NAT
5.3.2.2 Restricted Cone NAT
Restricted cone NAT maps all requests from the same private IP address and port to the same
public IP address and port. In contrast to full cone NAT, a host on the Internet can only send a
packet to the private IP address and port if the private IP address and port has previously sent a
packet to that host. In the following figure, if A has sent a packet to B, then B can send packets
to A and B’s source port can vary. C cannot send packets to A because A never sent a packet
to C.
Figure 17 Restricted Cone NAT
5.3.2.3 Port Restricted Cone NAT
Port restricted cone NAT is like a restricted cone NAT, but port numbers are included in the
restriction. In the following figure, B can send packets, with source IP address e.f.g.h and port
20202 to A because A previously sent a packet to IP address e.f.g.h and port 20202. B cannot
send packets, with source IP address e.f.g.h and port 10101 to A because A has not sent a
packet to IP address e.f.g.h and port 10101.