LAT Node and Service Names

Document ID: 9346

Introduction

This document provides example of how local-area transport (LAT) node and service names are used with Cisco IOS®. The examples also demonstrate how LAT connections can be monitored.

Before You Begin

Conventions

For more information on document conventions, see the Cisco Technical Tips Conventions.

Prerequisites

There are no specific prerequisites for this document.

Components Used

This document is not restricted to specific software and hardware versions.

LAT Requirements

In order for a router to automatically be aware of LAT service advertisements from other nodes, it must have the following setup:

• a Cisco IOS software image that supports LAT


• LAT enabled on the appropriate interfaces

Examples of these requirements are shown below:

  hopper# show version
  Cisco Internetwork Operating System Software
  IOS (tm) 2500 Software (C2500-J-L), Version 11.2(12.1), MAINTENANCE INTERIM SOFTWARE
  Copyright (c) 1986-1998 by cisco Systems, Inc.
  Compiled Mon 02-Mar-98 15:01 by cuser
  Image text-base: 0x0303F1BC, data-base: 0x00001000
  hopper# show lat service
  Service Name Rating Interface Node (Address)
  ALBIE 84 Ethernet0 ALBIE (aa00.0400.0a28)
  Ident: Welcome to OpenVMS VAX V7.1
  ALFIE 67 Ethernet0 ALFIE (aa00.0400.1728)
  Ident: Welcome to OpenVMS (TM) VAX Operating System, Version V7.1
  ALPHIE 71 Ethernet0 ALPHIE (0800.2be6.9ec9)
  Ident: @sys$manager:announce.txt

Because LAT is a valid input and output transport for the async ports, the router will respond to LAT solicitations directed at the router as long as LAT is configured as a valid transport. An example is shown below:

  line 2 3
  transport input all
  hopper# show line 2
  Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns
  2 TTY 9600/9600 - - - - - 0 0 0/0
  Line 2, Location: "", Type: ""
  Length: 24 lines, Width: 80 columns
  Baud rate (TX/RX) is 9600/9600, no parity, 2 stopbits, 8 databits
  Status: Ready
  Capabilities: none
  Modem state: Ready
  Group codes: 0
  Modem hardware state: noCTS noDSR DTR RTS
  Special Chars: Escape Hold Stop Start Disconnect Activation
  ^^x none - - none
  Timeouts: Idle EXEC Idle Session Modem Answer Session Dispatch
  00:10:00 never none not set
  Idle Session Disconnect Warning
  never
  Modem type is unknown.
  Session limit is not set.
  Time since activation: never
  Editing is enabled.
  History is enabled, history size is 10.
  DNS resolution in show commands is enabled
  Full user help is disabled
  Allowed transports are lat pad v120 mop telnet rlogin nasi. Preferred is lat.
  No output characters are padded
  No special data dispatching characters

Making a LAT Connection

There are two methods of establishing a LAT connection.

Method 1: The device requests a connection to a service based on a service advertisement multicast that has been seen and cached. An example is shown below:

  hopper# show lat service
  Service Name Rating Interface Node (Address)
  ALBIE 84 Ethernet0 ALBIE (aa00.0400.0a28)
  Ident: Welcome to OpenVMS VAX V7.1
  ALFIE 65 Ethernet0 ALFIE (aa00.0400.1728)
  Ident: Welcome to OpenVMS (TM) VAX Operating System, Version V7.1
  ALPHIE 71 Ethernet0 ALPHIE (0800.2be6.9ec9)
  Ident: @sys$manager:announce.txt
Method 2: The device solicits a connection to a node name "x", containing a port named "y". In the following example, the VAX has a LAT device (LTA400) defined to connect to node "hopper", port "2".

  ALFIE> mc latcp show port lta400
  Local Port Name: _LTA400: Local Port Type: Application (Queued)
  Local Port State: Inactive
  Connected Link:
  Target Port Name: 2 Actual Port Name:
  Target Node Name: HOPPER Actual Node Name:
  Target Service Name: Actual Service Name:

If a virtual terminal connection is attempted from the VAX, the following displays:

  ALFIE> set host/dte lta400
  %REM-I-TOQUIT, connection established
  Press Ctrl/\ to quit, Ctrl/@ for command mode
And this displays:

  hopper# debug lat event
  LAT event debugging is on
  hopper#
  hopper#
  00:18:06: LAT: Host Initiated connection from ALFIE to :2, sc=1
  00:18:06: LAT2: created new inbound session
  00:18:06: LAT2: Host-initiated connection complete
  00:18:06: LAT2: DataB: +FlowIn +FlowOut Parity 2A Mode Interactive(0) Speed *19200/*19200
  00:18:06: LAT2: DataB ignored
  hopper# who

As you can see, the router has taken the default node name of "hopper" (LAT is not case-sensitive), which is the host name of the router. You can also assign a different node name to the router using the lat node-name command, as shown below:

  hopper# conf terminal
  Enter configuration commands, one per line. End with CNTL/Z.
  hopper(config)# lat node-name froggie
  hopper(config)# ^Z

If the VAX now tries to connect, the router does not respond to the solicit request from the VAX, because the router no longer contains the LAT node name "hopper". The LTA device on the VAX needs to be redefined to point to the node name "froggie" instead of "hopper".

  ALFIE> set h/dte lta400
  %REM-I-TOQUIT, connection established
  Press Ctrl/\ to quit, Ctrl/@ for command mode
  %REM-E-PORTRXERR, port receive error
  -SYSTEM-F-HANGUP, data set hang-up
  %REM-S-END, control returned to node ALFIE
  %SYSTEM-F-HANGUP, data set hang-up%SYSTEM-F-HANGUP, data set hang-up
  ALFIE>
  hopper# show debug
  LAT:
  LAT event debugging is on
  hopper#
You can define services on the router to avoid the administrative overhead of node names. The configuration for this is shown below:

  hopper# conf terminal
  Enter configuration commands, one per line. End with CNTL/Z.
  hopper(config)# lat service rodent enab
  hopper(config)# ^Z
The router will now send out LAT service advertisements for the service "rodent". As shown in the example below, the VAX can see these service advertisements and is able to open connections using the service name:

  ALFIE> mc latcp show service

  ALFIE>set h/lat rodent
  %LAT-S-CONNECTED, session to RODENT on node FROGGIE established
  %LAT-I-TODISCON, type ^\ to disconnect the session
  User Access Verification
  Username:
  hopper#
  hopper#
  00:26:10: LAT: Host delay = 4 tics
  00:26:10: LAT: Got new inbound host connection
  00:26:10: LAT10: created new inbound session
  hopper#
Note: The methods of connection to a service name and to a node/port pair differ. The service connection provides a vty session while the node/port combination provides a TTY connection. This is because a service connection is initiated by the VAX to the access server, but a node/port connection is initiated by the access server as a result of an invitation from the VAX. The VAX actually asks the access server to start a Virtual Circuit from node "x" and port "y" to the VAX

An example of a service connection is shown below:
  hopper# who

An example of a node/port combination connection is shown below:

  hopper# who

Related Information

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