Application Note




        Interoperability between IP Switching and Classical IP





General Purpose Statement

It is expected that some networks will have legacy IP over ATM devices 
that do not support IP Switching.  To have interoperability between these 
legacy devices and IP Switching, RFC 1483 SNAP/LLC encapsulation is
implementated.  This document will describe the necessary procedure.



Application Overview

To achieve interoperability between legacy IP over ATM devices and IP 
Switching, a PVC must be created between the device and the IP Switch.  
This involves creating a logical interface on the IP Switch Gateway.  This
interface must be assigned a vpi and vci.  This device must then be 
configured.  The following steps document this.

1. At the prompt on the IP Switch Gateway enter:

        cd /usr/ips                             ***Changes to directory

        ./ addif pvcif-59 up atm-s1p1c0 0 59    *** configures interface, 
                                                    vpi, vci


2.  Do an ifconfig -a at the prompt and you will see a logical interface 
    created with the name pvcif-59

3.  This interface now needs to be configured with an IP address just as
    the other interfaces would be from the prompt.

        ifconfig pvcif-59  xx.xx.xx.xx   zz.zz.zz.zz   *** configure chosen
                                                           IP address


NOTE:  xx.xx.xx.xx = ip address of logical interface
             zz.zz.zz.zz  =  ip address of clip  station on opposite 
                             end of pvc

This ip address must be in the same subnet as the clip station which will
be used on the opposite end of the pvc.


4.  PVC configuration must be made on the GIGAswitch/ATM.   At the
    GIGAswitch/ATM prompt type OBM.


        Choose option #2 for Virtual Circuit Configuration Menu

        Choose option #2 for Set VCI Configuration Menu

        Choose option #1 for Connect Point-to-Point Circuit

                Enter desired slot for input:
                Enter desired port for input:
                Enter input vci:    59                     ***recommended vci

                Enter desired slot for output:
                Enter desired port for output:
                Enter output vci:    59                    ***recommeneded vci

                Enter desired CBR bandwidth, in Megabits/sec
                Zero will create a ABR circuit:
                Should this be a duplex circuit:  yes

                Commit permanent virtual circuit to non-volatile storage:  yes


At this point, the pvc is created on the GIGAswitch/ATM.




5.  A PVC must now be created on the CLIP station that you are using.  This is
    done by following the procedure for setting up PVC as documentated by the
    operating system in use.  (NT, Unix)

                ***recommended vpi,vci = 0,59



6.  Default routes must be set up on Ipswitch Gateways/Controller.




If this procedure has been followed correctly, interoperability between the
Ipswitch and Clip station will now exist.