User's Manual

Key Concepts 105
Once 3Com Network Director completes its additional discovery it then
updates the main database (and subsequently the map) with the newly
discovered information. It does this by comparing the information that
exists in the main database with that in the new, temporary database.
The basic rules it applies, when updating the main database, are as
follows:
■ Any new subnets are simply added to the new database as they would
be on an initial discovery
■ Any new devices are simply added to the appropriate subnets (either
existing or new).
■ Any devices that have changed (e.g. unit added/removed) are updated
– you can view their new details using the Properties dialog box.
■ Devices that exist in the main database but have been removed from
the network and/or simply did not respond in the second discovery
will not be deleted from the database or the map. The exception to
this is if a device’s IP address now belongs to another device. For
example: device A initially has address x, device B has address y. On a
subsequent discovery device A now has both addresses x and y. In this
scenario device A’s information will be updated to reflect its new
addresses and device B will be deleted.
■ Any new links (that is, connections between devices and/or device’s
ports) detected by the topology process will be added to the relevant
devices on the map.
■ If a port previously had a link to a device and that port is subsequently
detected as being connected to a different device, the old link will be
deleted and the new one created. A port can only be connected to
one other node.
■ If a port previously had a link and the second discovery could not
successfully establish that the same port was connected (for example,
3Com Network Director lost communication part way through) then
that link will not be deleted. Instead it will be marked as unconfirmed
and as a result will appear as a dashed line on the map.
Any changes detected as a result of additional discoveries are fully
described in the Changes report, automatically generated by 3Com
Network Director at the end of a rediscovery operation. See “
The
Changes Report” on page 133.