Brocade TurboIron 24X Series Configuration Guide - Manual (Page 404)

370 Brocade TurboIron 24X Series Configuration Guide
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VLAN overview
• Port-based VLAN – Affects all ports within the specified port-based VLAN.
STP is a Layer 2 protocol. Thus, you cannot enable or disable STP for individual protocol VLANs or
for IP subnet, IPX network, or AppleTalk cable VLANs. The STP state of a port-based VLAN
containing these other types of VLANs determines the STP state for all the Layer 2 broadcasts
within the port-based VLAN. This is true even though Layer 3 protocol broadcasts are sent on Layer
2 within the VLAN.
It is possible that STP will block one or more ports in a protocol VLAN that uses a virtual routing
interface to route to other VLANs. For IP protocol and IP subnet VLANs, even though some of the
physical ports of the virtual routing interface are blocked, the virtual routing interface can still route
so long as at least one port in the virtual routing interface protocol VLAN is not blocked by STP.
If you enable Single STP (SSTP) on the device, the ports in all VLANs on which STP is enabled
become members of a single spanning tree. The ports in VLANs on which STP is disabled are
excluded from the single spanning tree.
For more information, refer to Chapter 21, “Configuring Spanning Tree Protocol (STP) Related
Features” .
Virtual routing interfaces
A virtual routing interface is a logical routing interface that devices use to route Layer 3 protocol
traffic between protocol VLANs.
Devices send Layer 3 traffic at Layer 2 within a protocol VLAN. However, Layer 3 traffic from one
protocol VLAN to another must be routed.
If you want the device to be able to send Layer 3 traffic from one protocol VLAN to another, you
must configure a virtual routing interface on each protocol VLAN, then configure routing
parameters on the virtual routing interfaces. For example, to enable a Layer 3 Switch to route IP
traffic from one IP subnet VLAN to another, you must configure a virtual routing interface on each IP
subnet VLAN, then configure the appropriate IP routing parameters on each of the virtual routing
interfaces.
Figure 40 shows an example of Layer 3 protocol VLANs that use virtual routing interfaces for
routing.