Vlan Spanning Multiple Stpds - Extreme Networks ExtremeWare 7.2e Installation And User Manual

Spanning Tree Protocol (STP)
Figure 32: Tag-based STP configuration
Marketing & Sales Marketing, Sales & Engineering
Switch 1 Switch 3
Switch 2
Sales & Engineering
ES4K023
The tag-based network in Figure 32 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 must be configured on all ports in that domain, except
for ports that connect to hosts (edge ports).

VLAN Spanning Multiple STPDs

Traditionally, the mapping from VLANs to STP instances have been one-to-one, or many-to-one. In both
cases, a VLAN is wholly contained in a single instance. In practical deployment there are cases in which
a one-to-many mapping is desirable. In a typical large enterprise network, for example, VLANs span
multiple sites and/or buildings. Each site represents a redundant looped area. However, between any
two sites the topology is usually very simple.
200 ExtremeWare 7.2e Installation and User Guide