User's Manual

Useful Information and References 141
time if it or the network is very busy, or potentially may not receive, or be
able to respond to, the ICMP ping message if it is placed beyond a
firewall. If a device fails to respond to a ping then 3Com Network
Director will not add it in to the map as an IP device (although it may still
be added as a MAC-only device).
If a device responds to a ping, 3Com Network Director then attempts to
determine if it supports other protocols, in particular SNMP. See “
Device
Capability Detection ” on page 93. If the device supports SNMP, it reads
the IP address table to establish if the device has any additional IP
addresses. If any of those addresses conflict with the addresses of another
device then one of the two nodes may be discarded.
It is possible to inadvertently assign duplicate IP addresses to some
devices. Certain 3Com devices provide resilient management by allowing
you to assign an IP address to each of the units in a stack. If you
reconfigure your network and move a unit from one stack to another, if
the unit has been assigned an IP address, then that address will move
with it. If you do not want the address to move you should delete the IP
address from the unit when you transfer it.
Some devices are the wrong type
SNMP-capable devices can appear as generic IP icons on the map if the
wrong read community string was specified for the device or if SNMP
requests to the device timed-out.
If a device appears as a generic SNMP icon it usually means that 3Com
Network Director does not recognize the sysObjectID returned by the
device. 3Com Network Director only recognizes a limited number of third
party sysObjectIDs.
All 3Com devices should be recognized by 3Com Network Director.
However, for new devices that have been released after the version of
3Com Network Director you are using, the devices may be shown as
Generic SNMP or 3Com Device. In this case you should check the 3Com
web site for 3Com Network Director service packs that support these
newer devices.
There are clouds in my map
If 3Com Network Director cannot deduce exactly how devices are
connected together it sometimes creates clouds during topology process.
This is quite common with third party devices, particularly hubs. Wireless