Zyxel-communications 2002 Series Uživatelský manuál stáhnout pdf (Strana 44)

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.

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Zyxel-communications 2002 Series Uživatelský manuál Strana 44