Dell FCX624-S Laptop User Manual


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PowerConnect B-Series FCX Configuration Guide 437
53-1002266-01
VLAN overview
13
To direct individual ports or on a range of ports to this tag profile, enter commands similar to the
following.
PowerConnect(config)# interface ethernet 1/1/1
PowerConnect(config-if-e1000-1/1/1)# tag-profile enable
PowerConnect(config-mif-1/1/1,1/2/1)# tag-profile enable
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.
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 8, “Configuring Spanning Tree Protocol (STP) Related
Features”.
Virtual routing interfaces
A virtual routing interface is a logical routing interface that Layer 3 Switches use to route Layer 3
protocol traffic between protocol VLANs.
Dell PowerConnect 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.