This information applies to addresses entered for ATM;LAN emulation;
Classical IP and ARP over ATM; and IPX and ARP over ATM.
ATM-LLC Multiplexing
Protocols that run natively over an ATMinterface can use ATM-LLC multiplexing to
share ATMaddresses and both SVC and PVC channels between users. ATM-LLC
is implicitly configured when the protocols are configured and can be monitored
using the ATM Config+ command prompt from t5. There are no explicit
configuration options for the ATM-LLCmultiplexing function. For example, if two
protocols which use ATM-LLCmultiplexing are configured to use the same local
ATM address (local endpoint), this implicitly configuresATM-LLC to use the same
shared ATMaddress for both protocols.
See “ATM-LLC Monitoring Commands”on page 290 for additional information.
Sharing of ATMaddresses or SVC/PVC channels is not possible between protocols
that use the ATM-LLCmultiplexing function and those that do not use the ATM-LLC
multiplexing function (such as Classical IP). Currently, Server Cache
Synchronization Protocol (SCSP) and APPN are the only two protocols that use the
ATM-LLC multiplexing function.
ATM Virtual Interface Concepts
An ATMVirtual Interface (AVI) creates the appearance of multiple ATM interfaces
when, in fact, there is only one physical ATMinterface. One or more AVIs can be
configured for each physical ATMinterface on the router. AVIs have the following
characteristics:
vEach AVImust be defined on one (and only one) physical ATM interface. ATM
real interface (ARI) will be used to mean a physical ATMinterface.
vOne or more AVIscan be configured on each ARI on a router.
vHigher layer protocols treat ARIs andAVIs equally. The protocols see the total
number of ATMinterfaces as the sum of the number of ARIs and AVIs configured
on the router.
vProtocols can be configured on each ATMinterface (real or virtual) independently
of other interfaces.
For example, one can configure IP on interface 0 (which is a real ATMinterface)
with IP address 9.1.1.1 and another instance of IP with address 9.2.1.1 on
interface 1 (which is an AVI).Whether an interface is a real ATM interface or a
virtual interface configured on a real interface makes no difference to the protocol
(IP in the example). In addition, whether virtual interface 1 is configured on top of
real ATMinterface 0 or some other physical ATM interface is also transparent to
the protocols.
Advantages of Using ATM Virtual Interfaces
Major advantages of using the ATMVirtual Interfaces are:
vUsing the ATMVirtual Interface feature increases the number of protocol
instances that can be supported on a physical ATMinterface.
The actual number of AVIsthat can be configured on an ARI is limited by
physical resources, such as memory, available on the router.The total number of

Configuring ATMand LAN Emulation

274 MRS V3.2 Software User’s Guide