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In this scenario, the IP addresses that are used for the PPP connection allow for
what is known as an ’Unnumbered Net.’ It is called this because no new
networks or IP addresses were created for the connection. The IP address of the
Ethernet connection to LCL400 (10.1.1.1) is used as the remote address for
RMT400. The IP address of the Ethernet connection to RMT400 (10.2.1.1) is
used as the remote address for LCL400.
v If a user other than RMTOFFICE or RMTGATEWAY dials in, then he or she
receives IP address 10.1.1.99. This is accomplished by using the wildcard user
entry * (asterisk), which indicates that if the caller’s user ID is not found in the
list, then this IP address is used as the default. This action assumes the user has
been previously added to the OFFICE_400 validation list.
In the scenario, the remote user receives 10.1.1.99 as the IP address. He or she
also has access to the 10.1.1.0 network with no additional routing required.
Note: 10.1.1.99 has a subnet mask of 255.255.255.255 and is a subset of the
local 10.1.1.0 network. This is known as ″transparent subnetting″ (also
known as Proxy ARP) and allows for the remote user to appear to be on
the same Ethernet network that is attached to LCL400. See the example
in “Example: Remote LAN Access with Transparent Subnetting” on
page 104 for additional information about transparent subnetting.
If only explicitly defined callers can dial in, then you should omit the * entry. All
other callers are then denied access to LCL400.
Configuring RMT400 to Dial into LCL400
Access Point-to-Point functions through Operations Navigator.
From the General page, perform the following tasks:
v Specify a profile name (RMT400 for this example).
v Select PPP as the ″Type.″
v Specify Switched line-dial as the ″Mode.″
v You have the option of specifying a description.
From the Connection page, perform the following tasks:
v In this example, the phone number to connect to LCL400 is 798-1234. The -
(dash) is optional.
v Select an existing PPP line from the drop-down box and click Open. In this
example, the line 400DIAL is used.
If an existing line does not exist, you can create a new one by specifying the
name and clicking New.
v From the Modem page on the Line Properties dialog, select a modem from the
modem name pull-down box and click OK.
From the Authentication page, perform the following tasks:
v Select ″Enable local system identification.″
v Ensure that CHAP only is selected.
v The user ID that will be used to identify RMT400 when it dials a remote system
is RMTOFFICE.
Note: The user ID and password
must
be the same as those that you defined in
the OFFICE_400 validation list on LCL400.
Chapter 4. Configuring Point-to-Point TCP/IP (PPP and SLIP) 103