Alcatel SPEED TOUCH PRO, User Manual

Page: 164 / 238

Introduction
PPP & IP Routing
CIP & IP Routing
Consequences of
NA(P)T on layers
12 Networking Services - IP
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3EC 17059 ABAA TCZZA Ed. 01
12.6.2 Packet Services and NA(P)T
The STPro supports NA(P)T to be used in combination with:
PPP & IP Routing
CIP & IP Routing.
You can enable/disable NA(P)T via the 'PPP Configuration' page
per PPP entry.
In the
'Routing' box (See subsection 9.4.3) it is possible to
check/uncheck the NAT flag ( ). This allows the STPro to
decouple your local IP addresses from the public IP address
negotiated during a session.
You can enable/disable NA(P)T for each IP address of type CIP via
the CLI. This allows the STPro to decouple the explicit assigned or
implicit assigned IP addresses from your local network
configuration. That way, the STPro is able to act as a genuine LIS
member and to route between the CIP LIS and your LAN.
The NA(P)T feature comes at the expense of the STPro
transparency. This because a number of protocols that are layered
on top of either TCP/IP or UDP/IP do not adhere to the ISO/OSI
reference model.
Note : The ISO Open Systems Interconnection (OSI) reference model promotes
the layered implementation of communications protocol stacks. Layers from
protocol stacks implemented according to this model can be changed without
affecting the upper or lower layers.
An important consequence is that changing IP addresses or
TCP/UDP ports via NA(P)T affects the other layers as well.
Due to these changes, applications that are the ultimate
consumers of the protocols cannot decode the information
correctly anymore.