User's Manual

544 CHAPTER 13: VLAN MANAGEMENT
Figure 291 VLAN with Gaps
As well as checking for gaps such as this, 3Com Network Director also
assumes that for a VLAN to be complete it should be possible for devices
on this VLAN to communicate with devices on other VLANs and
vice-versa. This means that the switches on which the VLAN is to be
created should include at least one Layer 3 switch that is capable of
performing VLAN-based IP routing. See“
Communication between
VLANs” on page 504. If there is no such Layer 3 switch in the selected
switches, 3Com Network Director will find the nearest suitable Layer 3
switch and work out which switch ports would need to be added to the
VLAN to connect this Layer 3 switch to the other switches in the VLAN.
3Com Network Director will not search beyond clouds in the map when
trying to locate the nearest suitable Layer 3 switch. If you are adding a
VLAN to a set of devices where there is no path in the map from the
devices to a Layer 3 switch, 3Com Network Director will be unable to
determine which switch ports would need to be added to the VLAN in
order to connect a Layer 3 switch to the other switches in the VLAN.
For example, in the network below if the Create VLAN wizard was
launched with the switch2-switch3, switch3-switch4 and the switch4-PC
links selected, 3Com Network Director would spot the fact that there was
no Layer 3 switch in the selection. 3Com Network Director would then
find the nearest Layer 3 switch, L3switch, and determine that the ports
connecting L3switch to switch1, and the ports connecting switch1 and
switch2, should also be added to the new VLAN.