Nokia M10 - Manual (Page 143)

How your Nokia M10 works
DRAFT
E Copyright Nokia Telecommunications Oy NTC C33539002SE_A0 6-3
addresses. The table entries are also automatically deleted in case the
specific address is not detected behind the interface during 10 minutes.
In bridge-only mode a single IP address can be allocated to M10 if a
remote management of the M10 is required. The LAN IP address acts
as a host IP address in this case.
6.4 Network Address Port Translation (NAPT)
Network Address Port Translation (NAPT) or Network Address
Translation (NAT) is used to save IP addresses. When NAPT is
enabled the router has only one global IP address (per ATM channel).
The LAN port uses private IP addresses which are not seen outside the
router (typically 10.0.0.0 or 192.168.x.x). In normal operation NAPT
translates the IP addresses and TCP/UDP socket/port numbers
between the LAN and WAN interface.
NAPT router
192.168.1.254
195.1
12.12.161
src:192.168.1.112:1228
dst:194.112.11.111:80
src:194.112.11.111:80
dst:192.168.1.112:1228
src:195.112.12.161:1234
dst:194.112.11.111:80
src:194.112.11.111:80
dst:195.112.12.161:1234
Home network (LAN) Internet (WAN)
Figure 6-1 Network Address Port Translation
Normally, when host in the home network sends a packet to the
Internet the NAPT adds timestamp, protocol (e.g. TCP, UDP), IP
source address and source socket number as well as the IP destination
address and the destination socket number into the database. The
NAPT creates a new free socket number and replaces the original IP
source address and source socket number. When a reply is received
from WAN the same table is used to map the IP destination address and
destination socket number back to the original one. The entries from
the NAPT cache/table are removed when the entry timeouts.