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X.25 Protocols

Accepting Incoming PAD Calls without an X.25 Interface

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Document ID: 14189


Contents

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
Background Information
Configure
      Network Diagram
      Configurations
Verify
Troubleshoot
      Troubleshooting Commands
      Incoming XOT Call
      Disconnecting the Call
Related Information

Introduction

This sample configuration allows you to accept packet assembler/disassembler (PAD) calls and forward them to the right async lines when you do not have any X.25 interfaces configured on the router.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This configuration was developed and tested using Cisco IOS® Software Release 12.1(7).

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

For more information on document conventions, refer to Cisco Technical Tips Conventions.

Background Information

To accept PAD calls and forward them to the right async lines when you do not have any X.25 interfaces configured on the router, use the following commands:

  1. Run the pad from-xot command in global configuration mode.

  2. To forward the call to the correct async line, you must use subaddressing. Use the x25 host <hostname> <x121> command to determine the main address (all digits after the command are the subaddress).

  3. By using the rotary <subaddress> command on the specific lines, you can tell the router which line it has to forward the pad session on.

    Note: Only two digits are available for this.

For more information on these commands, refer to X.25 and LAPB Commands.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: To find additional information on the commands used in this document, use the Command Lookup Tool (registered customers only) .

Network Diagram

This document uses this network setup:

xot_incoming.gif

Configurations

Router A

 
service pad from-xot            

!--- allow incoming XOT call

service timestamps debug datetime msec
service timestamps log datetime msec
!
hostname router
!
enable password 
!
x25 routing
!
!
interface Serial1
 description IP connection getting the XOT call
 ip address 172.17.200.2 255.255.255.252
!
x25 host router 901         

!--- Map X25 address to accept call(use the Hostname)

!
line con 0
 exec-timeout 0 0
 password 
 length 0
 transport input none
line aux 0
 exec-timeout 0 0
 rotary 4                       

!--- sub address 04 point to aux line

 autocommand  x28               

!--- enable x28 for pad session

line vty 0 4 password 
 login
!
end

Verify

This section provides information you can use to confirm your configuration is working properly.

Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.

  • show line—check the line status. We are using aux 0 to tty1.

  • show host—check if the X.25 map address to hostname is correct.

  • show x25 vc—check the X.25 over TCP (XOT) virtual circuit (VC).

  • show x25 pad—check the X.3 parameters negotiated.

The output shown below is a result of entering these commands on the devices shown in the network diagram above.

router#show line
 Tty Typ     Tx/Rx    A Modem    Roty AccO AccI Uses  Noise  Overruns     Int
 *   0 CTY                 -   -      -    -     -     0       0       0/0      -
 *   1 AUX   9600/9600     -   -      4    -     -     8       2      0/373318  -
     2 VTY                 -   -      -    -     -    13       0       0/0      -
     3 VTY                 -   -      -    -     -     0       0       0/0      -
     4 VTY                 -   -      -    -     -     0       0       0/0      -
     5 VTY                 -   -      -    -     -     0       0       0/0      -
     6 VTY                 -   -      -    -     -     0       0       0/0      -
   
   router#show host 
   Default domain is not set
   Name/address lookup uses static mappings
   
   Host                        Flags      Age Type   Address(es)
   router                      (perm, OK) **  X.121  901
   
   router#show x25 vc
   SVC 1,  State: D1,  Interface: [172.17.200.1,11030/172.17.200.2,1998]
     Started 00:00:15, last input never, output never
     
     Line: 1   aux 0    Location:  Host: 900
     900 connected to 90104 PAD <--> XOT 172.17.200.1,11030
   
     Window size input: 2, output: 2
     Packet size input: 128, output: 128
     PS: 0  PR: 0  ACK: 0  Remote PR: 0  RCNT: 0     RNR: no
     P/D state timeouts: 0  timer (secs): 0
     data bytes 0/0 packets 0/0 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
   
   router#show x25 pad
   tty1, Incoming PAD connection 
   Total input: 0, control 0, bytes 0, drops 0. Input Queued: 0 of 7 (0 bytes).
   Total output: 0, control 0, bytes 0. Output Queued: 0 of 5.
   Flags: 0,   State: 3,   Last error: 1
    ParamsIn:  1:0, 2:0, 3:0, 4:0, 5:0, 6:0, 7:0,
       8:0, 9:0, 10:0, 11:0, 12:0, 13:0, 14:0, 15:0,
       16:0, 17:0, 18:0, 19:0, 20:0, 21:0, 22:0,
    ParamsOut:  1:1, 2:1, 3:126, 4:0, 5:1, 6:2, 7:2,
       8:0, 9:0, 10:0, 11:14, 12:1, 13:0, 14:0, 15:0,
       16:127, 17:24, 18:18, 19:2, 20:0, 21:0, 22:0,
   
   router#show debug
   General OS:
     Modem control/process activation debugging is on
   X.29 PAD:
     X25 PAD debugging is on
   X.25:
     X.25 special event debugging is on

Troubleshoot

This section provides information you can use to troubleshoot your configuration.

Troubleshooting Commands

Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.

Note: Before issuing debug commands, refer to Important Information on Debug Commands.

  • debug modem—observe modem line activity on server.

  • debug pad—shows debugging for all PAD connections.

  • debug x25 event—monitor all X.25 traffic.

Incoming XOT Call

The following debug output is produced in connection with incoming XOT calls:

*Mar  6 22:19:19.484: pad_ctxt_up: id 4DE1C0, 
reason 1F6C6 (event 0, impetus 10)
*Mar  6 22:19:19.492: [172.17.200.1,11029/172.17.200.2,1998]: 
XOT I P/Inactive Call (19) 8 lci 1
*Mar  6 22:19:19.496:   From (3): 900 To (5): 90104
*Mar  6 22:19:19.500:   Facilities: (6)
*Mar  6 22:19:19.500:     Packet sizes: 128 128
*Mar  6 22:19:19.504:     Window sizes: 2 2
*Mar  6 22:19:19.504:   Call User Data (4): 0x01000000 (pad)
*Mar  6 22:19:19.512: PAD: incoming call to busy rotary line 1
*Mar  6 22:19:19.516: Accepting call for line in X.28 mode
*Mar  6 22:19:19.520: [172.17.200.1,11029/172.17.200.2,1998]: 
XOT O P3 Call Confirm (11) 8 lci 1
*Mar  6 22:19:19.524:   From (0):  To (0): 
*Mar  6 22:19:19.528:   Facilities: (6)
*Mar  6 22:19:19.528:     Packet sizes: 128 128
*Mar  6 22:19:19.532:     Window sizes: 2 2
*Mar  6 22:19:19.532: PAD1: Call completed
*Mar  6 22:19:19.536: TTY1: pause timer type 1 (OK)

Disconnecting the Call

The following debug output is produced when you disconnect the call:

 *Mar  6 22:19:46.152: PAD1: Control packet received.
 *Mar  6 22:19:46.156: PAD1: Input X29 packet type 1 (Inv to clear) 
 len 1 Invite Clear
 *Mar  6 22:19:46.160: TTY1: resume timer type 1 (OK)
 *Mar  6 22:19:46.164: TTY1: no timer type 4 to destroy
 *Mar  6 22:19:46.164: PAD: Connection closed Cause: 0 Diag: 0
 *Mar  6 22:19:46.168: [172.17.200.1,11029/172.17.200.2,1998]: 
 XOT O P4 Clear (5) 8 lci 1
 *Mar  6 22:19:46.172:   Cause 0, Diag 0 
 (DTE originated/No additional information)
 *Mar  6 22:19:46.172: pad_clear_TX: context 4F8668, packet 30F974
 *Mar  6 22:19:46.176: PAD1: Closing connection to .  In 1/1, out 0/0
 *Mar  6 22:19:46.212: <detached>: XOT I P6 Clear Confirm (3) 8 lci 1
 *Mar  6 22:19:51.696: TTY1: timer type 1 expired
 *Mar  6 22:19:51.696: TTY1: Exec-timeout disabled
 *Mar  6 22:19:51.700: TTY1: destroy timer type 1

Related Information

Updated: Jun 01, 2005 Document ID: 14189