Operation Manual

IP Masquerading
NetWAYS/ISDN – 3 Remote Access with NetWAYS/ISDN 35
NetWAYS/ISDN supports the ADSL protocols PPP over Ether-
net (PPPoE) and PPP over ATM (PPPoA). If FRITZ!Card DSL is
used for the connection to the ADSL line, either of these pro-
tocols can be used. If the computer is connected to ADSL
using an Ethernet adapter and an external ADSL modem,
then only PPPoE can be used. NetWAYS/ISDN comes with
two pre-configured locations for ADSL: “FRITZ!Card DSL” and
“ADSL Modem PPPoE”.
IP Masquerading
The IP masquerading module in NetWAYS/ISDN replaces the
source IP addresses in TCP, UDP and ICMP packets with the
official IP address assigned to NetWAYS/ISDN by the remote
system. NetWAYS/ISDN’s use of IP masquerading provides
the following advantages:
Each time the connection to the Internet Service Provid-
er is re-established after an inactivity timeout,
NetWAYS/ISDN is assigned a new IP address. Thanks to
IP masquerading, the computer’s routing table does not
need to be updated each time the official IP address
changes. The IP masquerading function always substi-
tutes the current official IP address for the source ad-
dress of packets traveling from the LAN to the Internet,
throughout the logical connection.
By default, IP masquerading prohibits all incoming TCP
connections. Incoming packets that have not been re-
quested by an application in the LAN are discarded.
This makes the local network more secure.
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