User's Manual

96 CHAPTER 4: DISCOVERING THE NETWORK
with that NBX chassis. This allows 3Com Network Director to identify the
existence of phones which would not normally be detected.
NBX phones can be configured to work with or without an IP address.
Those with just a MAC address will be added to the 3Com Network
Director map in the same subnet as the NBX chassis, i.e. the subnet
currently being discovered. Those phones that additionally have an IP
address are only added to the map if the subnet they belong to is
discovered as part of the current discovery operation.
Device Sizing
During this final discovery stage further details are obtained about
individual SNMP devices that have been discovered. This is done for
devices which 3Com Network Director knows how to interrogate further,
often using proprietary MIBs. Sizing basically means obtaining detailed
configuration information. Normally this includes:
■ determining the number of units in a stack or number of modules in a
chassis
■ their type and software version
■ the number and type of ports on each unit or module
■ and their link status
■ the VLANs configured on the device.
This stage is executed once only when all the other stages have been run
on all of the desired subnets. The reason for this is that during the other
discovery stages some IP addresses may have been discovered as separate
devices, but it is desirable for 3Com Network Director to display them as
a single device on the map. Typically this applies to devices, with their
own IP addresses, that can contain intelligent modules, also with their
own IP addresses. In particular this applies to routing modules, since they
tend to have IP addresses on subnets not known to the host device
chassis or stack. By communicating with the chassis and its intelligent
modules, 3Com Network Director can deduce that they are physically
part of the same chassis, and consequently merge them into a single
device on the map.
The Discovery Process
– Determining
Topology
The second part of the discovery process is to determine the topology of
a network, by establishing what links exist between the different devices
that have been discovered. The operation determines how the devices