3Com 3C15500 - Network Director - PC, User Manual

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94 C
HAPTER
4: D
ISCOVERING THE
N
ETWORK
the Web and Telnet menu options on the right-click menu. For certain
3Com devices additional information can be obtained using HTTP – see
“Web Type Recognition” and “NBX Phone Detection” on page 95
SNMP Type Detection
This stage only applies to devices that were found to support SNMP
during the Device Capability Stage. 3Com Network Director reads
standard SNMP MIBs in order to determine additional information about
each SNMP node, in particular the type of the device (based on MIB-II
sysObjectID), its IP addresses and its MAC addresses. Where a device has
multiple IP addresses that respond with the same information, e.g. list of
MAC addresses, 3Com Network Director ensures that it is represented as
a single device on the map. Certain devices which have multiple IP
addresses respond with different information. Initially they are detected
as separate nodes, which 3Com Network Director attempts to resolve in
the sizing stage.
If a router is detected when discovering a given subnet, that router
information will be made available to any subsequent subnets included as
part of the whole discovery operation. This ensures that the router is not
interrogated more than once for the same information by several stages.
IP to MAC Resolution
This stage is responsible for obtaining the MAC addresses of non-SNMP
nodes. For the local subnet, i.e. the one to which the 3Com Network
Director PC is attached, this is achieved by reading the ARP cache of the
3Com Network Director PC. For remote subnets this is achieved by
querying any routers that have been discovered on these subnets. This
stage is not normally required for determining the MAC addresses of
SNMP nodes, since that can be achieved in the SNMP type detection
stage.
It is important for 3Com Network Director to determine the MAC
addresses of nodes in order to be able to subsequently determine their
position in the network topology.
End Station Type Recognition
This stage is responsible for attempting to determine the operating
system type for devices that are IP-only or unrecognized (generic) SNMP.