User's Manual

100 CHAPTER 4: DISCOVERING THE NETWORK

devices may not support remote poll. If either the write community string

is not known for a device or it does not support remote poll then the

accuracy of the deduced topology may be reduced.

Outstanding end station stage

Not all end stations will be resolved by the Initial Endstation stage. For

instance, some ports may have multiple addresses in their bridge tables

even though only a single device is attached (if, for example, older

addresses not have aged out). Therefore a similar process to the Device

Resolution stage is used to locate the switches that have learned the

addresses of known end stations. As with the Device Resolution stage it

may not be necessary to communicate with all switches since their

address tables will have been cached from the previous stages.

Tree Building Stage

This does not require any device access. It is the point at which 3Com

Network Director analyzes all the information it has obtained from the

previous stages. It builds a tree view of the subnet/multinet, placing end

station devices appropriately. It also adds back in any blocked spanning

tree links.

Clouds – Unknown Topology

When 3Com Network Director builds the network tree, there may be

certain parts where it is unable to exactly determine the network

topology. In such cases you will see clouds on your map depicting the

areas of uncertainty. Typically these tend to be ports that have seen the

addresses of multiple devices, but those learned devices do not provide

any further topology information about the network.

For example, there may be a case where a switch port is connected to an

unmanaged hub, and that unmanaged hub is directly connected to two

end stations (e.g. PCs). The port on the first switch will learn the

addresses of the two end stations. It will not learn the address of the hub

(because it does not have one) and 3Com Network Director will not

detect the existence of the unmanaged hub because it won’t respond to

a ping. 3Com Network Director depicts this scenario as follows: