Brocade TurboIron 24X Series Configuration Guide - Manual (Page 403)

Brocade TurboIron 24X Series Configuration Guide 369
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VLAN overview
FIGURE 39 VLANs configured across multiple devices
Support for 802.1Q-in-Q tagging
Devices provide finer granularity for configuring 802.1Q tagging, enabling you to configure 802.1Q
tag-types on a group of ports, thereby enabling the creation of two identical 802.1Q tags
(802.1Q-in-Q tagging) on a single device. This enhancement improves SAV interoperability between
devices and other vendors’ devices that support the 802.1Q tag-types, but are not very flexible with
the tag-types they accept.
For example applications and configuration details, refer to “Configuring 802.1Q-in-Q tagging” on
page 407.
Spanning Tree Protocol (STP)
The default state of STP depends on the device type:
• STP is disabled by default on Layer 3 Switches.
• STP is enabled by default on Layer 2 Switches.
Also by default, each port-based VLAN has a separate instance of STP. Thus, when STP is globally
enabled, each port-based VLAN on the device runs a separate spanning tree.
You can enable or disable STP on the following levels:
• Globally – Affects all ports on the device.
NOTE
If you configure a port-based VLAN on the device, the VLAN has the same STP state as the
default STP state on the device. Thus, on Layer 2 Switches, new VLANs have STP enabled by
default. On Layer 3 Switches, new VLANs have STP disabled by default. You can enable or
disable STP in each VLAN separately. In addition, you can enable or disable STP on individual
ports.
User-configured port-based VLAN
T = 802.1Q tagged port
T T
T T
T
T
Segment 1
Segment 2
T
Segment 2 Segment 1
Tagging is required for the ports
on Segment 1 because the ports
are in multiple port-based VLANs.
Without tagging, a device receiving
VLAN traffic from the other device
would not be sure which VLAN the
traffic is for.
Tagging is not required for the ports
on Segment 2 because each port is
in only one port-based VLAN.