Ip Address Assignment - ZyXEL Communications P870HNU-51B User Manual

Chapter 5 WAN Setup

IP Address Assignment

A static IP is a fixed IP that your ISP gives you. A dynamic IP is not fixed; the ISP assigns you a
different one each time. The Single User Account feature can be enabled or disabled if you have
either a dynamic or static IP. However the encapsulation method assigned influences your choices
for IP address and default gateway.
Full Cone NAT
In full cone NAT, the NAT router maps all outgoing packets from an internal IP address and port to a
single IP address and port on the external network. The NAT router also maps packets coming to
that external IP address and port to the internal IP address and port.
In the following example, the Device maps the source address of all packets sent from the internal
IP address 1 and port A to IP address 2 and port B on the external network. The Device also
performs NAT on all incoming packets sent to IP address 2 and port B and forwards them to IP
address 1, port A.
Figure 33 Full Cone NAT Example
1, A
2, B
Symmetric NAT
The full, restricted and port restricted cone NAT types use the same mapping for an outgoing
packet's source address regardless of the destination IP address and port. In symmetric NAT, the
mapping of an outgoing packet's source address to a source address in another network is different
for each different destination IP address and port.
In the following example, the Device maps the source address IP address 1 and port A to IP
address 2 and port B on the external network for packets sent to IP address 3 and port C. The
Device uses a different mapping (IP address 2 and port M) for packets sent to IP address 4 and
D
port .
A host on the external network (IP address 3 and port C for example) can only send packets to the
internal host via the external IP address and port that the NAT router used in sending a packet to
111
P-870HNU-51b User's Guide