What Is The Difference Between Nat And Sua; How Many Network Users Does Sua/Nat Support; What Are Device And Protocol Filters - ZyXEL Communications P-2608HWL-D1 Support Notes

P-2608HWL Series Support Notes
source port in the TCP or UDP header with another value chosen out of a local pool. It then recomputed the
appropriate header checksums and forwards the packet to the Internet as if it is originated from Prestige using
the IP address assigned by ISP. When reply packets from the external Internet are received by the Prestige, the
original IP source address and TCP/UDP source port numbers are written into the destination fields of the
packet (since it is now moving in the opposite direction), the checksums are recomputed, and the packet is
delivered to the intended destination on the LAN. This is because SUA keeps a table of the IP addresses and
port numbers currently used by the LAN computers.

What is the difference between NAT and SUA?

NAT is a generic name defined in RFC 1631 'The IP Network Address Translator (NAT)'. SUA (Internet
Single User Account) is ZyXEL's proprietary implementation and trade name for the PAT feature which is a
specific type of NAT. SUA (or PAT for NAT) translates address into port mapping.
The primary motivation for RFC 1631 is that there is not enough IP addresses to go around. In addition, many
corporations simply did not bother to obtain legal (globally unique) IP addresses for their networks and now
finding themselves unable to connect to the Internet.
Basically, NAT is a process of translating one address to another. A NAT implementation can be as simple as
substituting an IP address with another. This allows a network to rectify the illegal address problem mentioned
above without going through each and every host.
The goal of ZyXEL's SUA design is to minimize the Internet access cost in a small office environment by using
a single IP address to represent multiple hosts on the LAN. It does more than IP address translation, so that
multiple hosts on the LAN can access the Internet at the same time.

How many network users does SUA/NAT support?

The Prestige does not limit the number of the users but the number of the sessions for Internet access. The
Prestige supports up to2048 sessions. You can view the current active sessions using the 'ip nat iface enif0 disp'
command in SMT menu 24.8.

What are Device and Protocol filters?

In ZyNOS, there are two filter groups: device filter and protocol filter. Generic filters belong to the device filter
group while TCP/IP and IPX filters belong to the protocol filter group.
148
All contents copyright (c) 2005 ZyXEL Communications Corporation.