ZyXEL Communications P-202 - Manual (Page 8)

P-202H Plus v2 Support Notes
b. To backup the SMT configurations, use TFTP client program to get file
'rom-0' from the P-202H Plus v2.
c. To restore the SMT configurations, use the TFTP client program to save
your configuration in file 'rom-0' in the P-202H Plus v2.
9. What should I do if I forget the system password?
In case you forget the system password, you can upload ROMFILE to reset the
SMT to factory default. After uploading ROMFILE, the default system password
is '1234'.
10. What is SUA? When should I use SUA?
SUA (Single User Account) is a unique feature supported by P-202H Plus v2
router which allows multiple people to access Internet concurrently for the cost of
a single user account.
When P-202H Plus v2 acting as SUA receives a packet from a local client
destined for the outside Internet, it replaces the source address in the IP packet
header with its own address and the source port in the TCP or UDP header with
another value chosen out of a local pool. It then recomputes the appropriate
header checksums and forwards the packet to the Internet as if it is originated
from P-202H Plus v2 using the IP address assigned by ISP. When reply packets
from the external Internet are received by P-202H Plus v2, 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 its true destination. This is
because SUA keeps a table of the IP addresses and port numbers of the local
systems currently using it.
11. 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 implementation and trade name
for functioning PAT (Port Address Translation) 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 address to go
around. In addition, great 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
All contents copyright © 2006 ZyXEL Communications Corporation.
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