User's Manual

Key Concepts 99
Initial Endstation stage
During this stage an attempt is made to identify the ports that have only
learned a single address. This is done by reading bridge address tables.
The purpose of this stage is two-fold:
■ to eliminate the need for many end station addresses having to be
considered in the rest of the topology, which can reduce the amount
of processing and network traffic generated in the remainder of the
topology process;
■ to detect the existence of non-IP (MAC-only) nodes. If a port has a
functioning link and has learned exactly one MAC address then that
address is assumed to be a single node attached to that port. If no IP
address was found to map to this MAC address during the IP to MAC
Resolution stage then 3Com Network Director will assume that this
MAC address belongs to a new node. Consequently 3Com Network
Director will show the MAC-only node on the map.
You may have deliberately instructed the discovery operation to only
detect IP ranges relevant to your switches which are outside the ranges of
your endstations. Consequently the depiction of MAC-only nodes may
not be required. You can prevent MAC-only nodes from being added to
your map by selecting the Only core devices or Only IP devices in the
Discovery Options pane of the Network Discovery Wizard. See “
Discovery
Options Pane” on page 122 for more information.
Device Resolution Stage
During this stage 3Com Network Director attempts to establish which
switches have learned the addresses of other switches, and on which
ports. Since some addresses have already been read from the bridge
tables in the previous stage, 3Com Network Director may not need to
communicate with all switches during this stage.
At the end of this stage, 3Com Network Director analyses whether it has
enough information to determine the network topology.
Remote Poll Stage (directed pings)
If insufficient information was obtained from the Device Resolution stage,
then an attempt is made to force devices to learn the addresses of others
by instructing them to ping each other (remote poll).
As with the previous remote poll stage the write community string of the
relevant switches is required. Also, as with the previous stage some