Atm Nbma; Arp Table; Static Map Versus Inverse Arp; Figure 2: Nbma Interface Stack - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - LINK LAYER CONFIGURATION GUIDE 2010-10-13 Configuration Manual

ATM NBMA

ARP Table

Copyright © 2010, Juniper Networks, Inc.
The software supports nonbroadcast multiaccess (NBMA) networks, which interconnect
more than two routers and have no broadcast capabilities.
NOTE: The E120 and E320 routers do not support ATM NBMA in the current
release.
An ATM NBMA network can be thought of as an interface stack with a single IP interface
at the top, eventually fanning out to multiple independent PVCs. See Figure 2 on page 13.

Figure 2: NBMA Interface Stack

Unlike standard point-to-point ATM interfaces and broadcast-oriented Ethernet interfaces,
NBMA interfaces form a point-to-multipoint connection. For example, you can use NBMA
to connect a router to multiple stations.
An NBMA interface consists of a single ATM 1483 subinterface that has two or more VCs.
You can add circuits to an existing ATM 1483 subinterface at any time. New circuits
become usable after they have valid ARP table entries. NBMA circuits support only IP
directly over ATM 1483.
The software restricts NBMA interfaces so that all circuits reside on the same physical
interface. An NBMA interface can use as many PVCs as are available on a physical port.
To maintain the Address Resolution Protocol (ARP) table, you can use either static
mapping via the CLI or Inverse ARP (InARP). InARP provides a way of determining the IP
address of the device at the far end of a circuit. For NBMA interfaces, InARP enables
automatic creation of ARP table entries for each circuit on the interface.
You must enable InARP when you create a PVC by using the atm pvc command. After
you configure InARP, a protocol mapping between an ATM PVC and a network address
is learned dynamically as a result of the exchange of InARP packets.

Static Map Versus Inverse ARP

If the device at the other end of a circuit does not support InARP, static mapping is required
for that circuit. One of these two methods must be used to generate an ARP table entry
for each circuit of the NBMA interface.
Chapter 1: Configuring ATM
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