Basic ATM Configuration

An ATM network represents two or more routers interconnected by ATM connections. Each router on the ATM network is connected to the ATM network by a Virtual Channel Connection (VCC). Each router is connected to a ATM switch that in turn connects to the ATM network. Each node on the ATM network is identified by a unique Virtual Path Identifier (VPI) and Virtual Connection Identifier (VCI) pair.

The interface or port used to connect the router to the ATM network is called a ATM interface and each ATM interface must have an IP address.
  • Each router is a node on the ATM network, identified by a unique VPI/VCI pair.
  • The ATM network has its own IP network number that is normally a class C or a subnet of a class C that is unique from other subnets on the system.
  • Each router ATM interface (port) is assigned an IP address from the ATM network's subnet, thus the netmask for each Frame interface on each router of the ATM network is the same.
  • VPI/VCI numbers are used to point from the ATM switch located at the telephone company central office, to the PVC of a router(s) on the other side of the ATM network.
====ETHERNET===================== ===
        | LAN IP:
|                |
|  Router A      |
|   Serial0      |
        | WAN IP:
       [-] CSU/DSU
        |ATM WAN
        |                            |
       [-] CSU/DSU                   | WAN IP:
        |                    +-------+-------+
        | WAN IP:|   Serial0     |
+-------+--------+           |  Router C     |
|   Serial0      |           |               |
|  Router B      |           +-------+-------+
|                |                   | LAN IP: 192.168.300.300
+-------+--------+  ===ETHERNET=======
        | LAN IP:
====ETHERNET===================== ===

Configuring IP Over ATM

The following is a sample of a port configuration: 
  • For this example: The ATM interface on the router is Serial0
  • For this example: The IP address of the ATM connection on the router is
# Comments (denoted by a hash mark at the beginning of the line)
# are permitted anywhere in the file
# See the Command Reference for more information on the
# commands below
version 2.00
interface Serial0
 description Port 0
 encapsulation atm
interface Serial0.1
 description UUNet T1
 encapsulation atm
 pvc 2/33
 ip address
ip route Serial0.1
At this point, ATM cells should be being transmitted and received. The status of the WAN port should change to up. It should now be possible to ping the other side. The interface statistics (Option 2 from the Main menu) should show:

19:03:17              Interface Summary                                Router A
#  Port      Description          Encaps       Bandwidth    HW  Proto  In   Out
 0 Ethernet0 100Mb Ethernet       Ethernet     100.00 Mbit  up   up     0%   0%
 1 Serial0   Port 0               ATM            1.54 Mbit  up   up     0%   0%
 2   Serial0.1   UUNet  T1                       1.54 Mbit  up   up     0%   0%
d - Detail  s - Sleep interval  q - Quit

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