3Com OfficeConnect 3C886A Release Note page 13

Understanding the
Three Dial-in
Scenarios
Before you can use the Dial-in Wizard to set up the LAN Modem for dial-in access,
it may help to understand the three dial-in scenarios available for each of your ten
authorized dial-in users. The scenarios are as follows.
Single User Dial-in (single modem or another 56K LAN Modem running NAT)
LAN Modem Site-to-Site Dial-in (LAN-to-LAN bidirectional connectivity)
Advanced Dial-in (unknown router accessing a LAN Modem)
Single User Dial-in
Single User Dial-in describes a scenario where a client workstation dials into a LAN
Modem via a single analog modem (or another 56K LAN Modem, see below).
With Single-User Dial-in the server-side LAN Modem assigns a single IP address to
the incoming client, as shown in Figure 5.
PWR TEST D B1 B2 SD RD DTR
Analog modem
Telecommuter
Figure 5 Single User Dial-in
Single-User Dial-in from Another 56K LAN Modem: While Single-User
Dial-in provides only one IP address to the dial-in client, the dial-in client may still
be another LAN Modem with several attached workstations. In this case, the
client-side LAN Modem uses NAT to share the single IP address provided by the
server-side LAN Modem, similar to a typical ISP connection, as shown in Figure 6.
Note that unlike the LAN Modem Site-to-Site scenario (described later), the Single
User scenario does not provide for bidirectional LAN-to-LAN connectivity. While
authorized workstations attached to the client LAN Modem can share the
connection to the server LAN Modem, workstations connected to the server LAN
Modem cannot access client-side resources.
Server
OfficeConnect
56K LAN Modem
Server side LAN
Figure 6 Single User Dial-in with NAT
Understanding the Three Dial-in Scenarios
Public telephone
3ComImpact IQ ¤ 3 Com
network
Telephone line
198.162.2.4 198.162.2.4
Public telephone
network
Server LAN Modem issues
single IP address to
incoming client
OfficeConnect
56K LAN Modem
Small office LAN
Client
OfficeConnect
56K LAN Modem
Client
Client LAN Modem
uses NAT to translate
Client side LAN
issued IP address
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