3Com OfficeConnect 3C891A, Release Note

Page: 13 / 24

Understanding the Three Dial-in Scenarios 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,
you should 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 (terminal adapter or 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 ISDN terminal adapter (or another 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.
Figure 5 Single User Dial-in
Single-User Dial-in from Another 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, 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.
Figure 6 Single User Dial-in with NAT
Public telephone
network
AL ER T
LA N S TA TU
S
PO WE R B1
B2 TX 1 2 3 4 CO LL
IS DN
OK
ISD N L AN M ode m 3C 892
Small office LAN
OfficeConnect
ISDN LAN Modem
ISDN BRI line
Terminal adapter
(ISDN modem)
Telecommuter
PWR TEST D B1 B2 SD RD DTR
3ComImpact IQ
¤ 3 Com
192.16
8.2
.2
192.16
8.2.3
Server side LAN
Client side LAN
OfficeConnect
ISDN LAN Modem
192.168.254.1 192.168.254.1
OfficeConnect
ISDN LAN Modem
Client
Server LAN Modem issues
single IP address to
incoming client
Client LAN Modem
uses NAT to translate
issued IP address
Public telephone
network
Client