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Basic Rate Interface (BRI) is an Integrated Systems Digital Network (ISDN) interface, and it consists of two B channels (B1 and B2) and one D channel. The B channels are used to transfer data, voice, and video. The D channel controls the B channels.
ISDN uses the D channel to carry signal information. ISDN can also use the D channel in a BRI to carry X.25 packets. The D channel has a capacity of 16 kbps, and the X.25 over D channel can utilize up to 9.6 kbps.
The X.25 on ISDN feature allows you to set the parameters of the X.25-over-D-channel interface without disrupting the original ISDN interface configuration. In a normal ISDN BRI interface, the D and B channels are bundled together and represented as a single interface. The original BRI interface will continue to represent the D, B1, and B2 channels.
Because some end-user equipment uses static terminal endpoint identifiers (TEIs) to access this feature, static TEIs are supported. The dialer understands the X.25-over-D-channel calls and initiates them on a new interface.
X.25 traffic over the D channel can be used as a primary interface where low-volume, sporadic interactive traffic is the normal mode of operation.
Supported traffic includes IPX, AppleTalk, transparent bridging, XNS, DECnet, and IP.
This feature is not available on the ISDN Primary Rate Interface (PRI).
This feature is supported on these platforms:
Configuring an ISDN BRI to carry the X.25 packets creates a separate interface, which can be configured separately from the parent ISDN interface. The dialer understands the X.25-over-D channel calls and initiates them on the new interface. The original BRI interface continues to represent the D, B1, and B2 channels.
Some countries (mostly European) and some switches in the United States (DMS-100) require that the end-user equipment use static TEIs in order to access this service.
To configure an ISDN BRI interface (and create a special ISDN interface) to carry X.25 traffic on the D channel, complete the following tasks beginning in global configuration mode:
| Task | Command |
|---|---|
| Step 1 Specify an ISDN BRI interface. | interface bri number |
| Step 2 Specify a static TEI, if required by the switch. | isdn x25 static-tei number |
| Step 3 Create a configurable interface for X.25 traffic over the ISDN D channel. | isdn x25 dchannel |
The new X.25-over-ISDN interface is called interface bri number:0 in configuration displays. It can be configured as an individual X.25 interface. The encapsulation x25 command is neither required nor used on this new interface, but other X.25 commands can be used to configure this interface. For more information about configuring an interface for X.25 traffic, refer to the Cisco IOS Release 11.2 Wide-Area Networking Configuration Guide.
If you want to remove the X.25-over-ISDN interface later, use the no isdn x25 dchannel command.
The following example creates a BRI 0:0 interface for X.25 traffic over the D channel and then configures the new interface to carry X.25 traffic.
interface bri0 isdn x25 dchannel isdn x25 static-tei 8 ! interface bri0:0 ip address 10.1.1.2 255.255.255.0 x25 address 31107000000100 x25 htc 1 x25 suppress-calling-address x25 facility windowsize 2 2 x25 facility packetsize 256 256 x25 facility throughput 9600 9600 x25 map ip 10.1.1.3 31107000000200
This section documents new commands. All other commands used with this feature are documented in the Cisco IOS Release 11.2 command references.
To create a configurable interface for X.25 traffic over the ISDN D channel, use the isdn x25 dchannel interface configuration command. To remove the interface, use the no form of this command.
isdn x25 dchannelThis command has no arguments or keywords.
Disabled
Interface configuration
This command first appeared in Cisco IOS Release 11.2 F.
This command creates a new, configurable interface, which can be specified as interface brix:0 in commands, where x is the original BRI interface number.
For example, on a Cisco 4500 router with an MBRI, if the isdn x25 dchannel command is configured on bri5, the new interface is bri5:0 and can be used for configuring the other parameters for X.25 over the D channel. These parameters include the addresses, the map statements, and others.
To display the new interface, use the show running config command.
The following example creates interface bri1:0 and configures it for X.25 over the ISDN D channel:
interface bri1 isdn x25 dchannel interface bri1:0 ip address 10.1.1.2 255.255.255.0 x25 address 31107000000100 x25 htc 1 x25 suppress-calling-address x25 facility windowsize 2 2 x25 facility packetsize 256 256 x25 facility throughput 9600 9600 x25 map ip 10.1.1.3 31107000000200 x25 map ip 10.1.1.4 31107000000800
interface bri
To configure a static ISDN Layer 2 terminal endpoint identifier (TEI) for X.25 over the ISDN D channel, use the isdn x25 static-tei interface configuration command. Use the no form of this command if dynamic TEIs will be used for X.25-over-D-channel interface.
isdn x25 static-tei tei-number| tei-number | Terminal endpoint identifier, in the range 0 to 63. |
Disabled
Interface configuration
This command first appeared in Cisco IOS Release 11.2 F.
This command applies to ISDN BRI interfaces only. Only one static TEI is allowed per BRI interface. If a second static TEI is configured, the first static TEI is overwritten.
Some switches require a static TEI be used for X.25 over the ISDN D channel.
When the isdn x25 dchannel command is invoked without the isdn x25 static-tei command, a dynamic TEI is chosen.
The following example creates static TEI 8 on the X.25-over-ISDN-D channel:
interface bri0 isdn x25 dchannel isdn x25 static-tei 8
The following example sets dynamic TEIs for the ISDN channel:
interface bri0 isdn x25 dchannel
interface bri
isdn x25 dchannel
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