Extreme Networks ExtremeWare XOS Guide Manual page 144

Spanning Tree Protocol (STP)
Figure 10: Tag-based STP configuration
Marketing & Sales Marketing, Sales & Engineering
Switch 1 Switch 3
Switch 2
Sales & Engineering
EX_049
The tag-based network in Figure 10 has the following configuration:
• Switch 1 contains VLAN Marketing and VLAN Sales.
• Switch 2 contains VLAN Engineering and VLAN Sales.
• Switch 3 contains VLAN Marketing, VLAN Engineering, and VLAN Sales.
• The tagged trunk connections for three switches form a triangular loop that is not permitted in an
STP topology.
• All VLANs in each switch are members of the same STPD.
STP can block traffic between switch 1 and switch 3 by disabling the trunk ports for that connection on
each switch.
Switch 2 has no ports assigned to VLAN marketing. Therefore, if the trunk for VLAN Marketing on
switches 1 and 3 is blocked, the traffic for VLAN Marketing will not be able to traverse the switches.
NOTE
If an STPD contains multiple VLANs, all VLANs should be configured on all ports in that domain, except
for ports that connect to hosts (edge ports).
144 ExtremeWare XOS 10.1 Concepts Guide