Nokia M11 T66220, User Manual

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How your Nokia M11 works
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Copyright Nokia Networks Oy C33833001SE_00
6-3
addresses. The table entries are also automatically deleted in case a
specific address is not detected behind the interface during 10 minutes.
In bridge-only mode, a single IP address can be allocated to M11 if a
remote management of M11 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 each 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 Principle of Network Address Port Translation
Normally, when the host in the home network sends a packet to the
Internet, the NAPT adds timestamp, protocol (for example 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.