Configuring legacy protocols Configure X.25 parameters
Digi TransPort® Routers User Guide
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n For ISDN D-channel operation, select the LAPD option is selected.
n For ISDN B-channel operation or operation through a synchronous port, select LAPB.
n For LAPB and LAPD, you can also specify an interface number.
This parameter specifies which LAPB or LAPD instance to use for the relevant TPAD instance.
Select 0 or 1 for LAPB or 0 or 1 for LAPD.
Use backup interface
A backup interface to use automatically if the call to the primary interface fails. The primary
interface is tried first for every new call attempt.
3. Set X.25 settings:
Default X.25 packet size
The default X.25 packet size. This can be set to 16, 32, 64128, 256, 512 or 1024, but the actual
values permitted are normally constrained by your service provider.
Answer incoming calls from NUA
The NUA that the router responds to for incoming X.25 calls.
Only answer calls with CUG
The PAD will only answer calls with this Call User Group (CUG) specified.
Use X.25 Call Macro macroname to an ATD command
The name of an X.25 call macro to use when the router receives an ATD command. The router
ignores the ATD command, replacing it with a PAD CALL command using the macro. The
purpose of this feature is to allow non-PAD terminals to use an X.25 PAD network connection.
To configure X.25 call macros, go to the Configuration > Network > Legacy Protocols > X.25
> Call Macros web page, or use the macro text command.
When making an outgoing call
Use NUA
The NUA to use as the calling NUA when the router makes an outgoing X.25 call.
LCN
The router supports up to 8 logical X.25 channels. In practice, the operational limit is
determined by the particular service to which you subscribe (usually 4). Each logical channel
must be assigned a valid Logical Channel Number (LCN). The LCN parameter is the value of the
first LCN that will be assigned for outgoing X.25 CALLs. The default is 1027.
For incoming calls, the router accepts the LCN specified by the caller.
LCN direction
Whether the LCN for outgoing X.25 calls is incremented or decremented from the starting
value when multiple X.25 instances share one layer 2 (LAPB or LAPD), connection. The default is
Down and LCNs are decremented, such as if the first CALL uses 1024, the next will use 1023,
etc. Setting the parameter to Up causes the LCN to be incremented from the start value.
NUI/NUA selection
If both an NUI and an NUA are included in the call string, this parameter allows the router to
filter one of these out of the X.25 call request. This can be extremely useful in backup
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