Configuring Advanced

Features

 

 

Configuring Advanced Features

Spanning Tree Protocol (STP)

C a u t i o n

The Fast Mode configuration should be used only on switch ports connected

 

to end nodes. Changing the Mode to Fast on ports connected to hubs, switches,

 

or routers may cause loops in your network that STP may not be able to

 

immediately detect, in all cases. This will cause temporary loops in your

 

network. After the fast start-up sequence, though, the switch ports operate

 

according to the STP standard, and will adjust their state to eliminate continu-

 

ing network loops.

 

 

To Configure Fast Mode for a Switch Port:

In the CLI, use this command: spanning tree mode <port list> fast

For example, to configure Fast mode for ports 1-3 and 5:

HP2512(config)# spanning-tree ethernet 1-3,5 mode fast

In the menu interface, go to the Main Menu and follow the steps under “Menu: Configuring STP” on page 9-103.

STP Operation with 802.1Q VLANs

As recommended in the IEEE 802.1Q VLAN standard, when spanning tree is enabled on the switch, a single spanning tree is configured for all ports across the switch, including those in separate VLANs. This means that if redundant physical links exist in separate VLANs, spanning tree will block all but one of those links. However, if you need to use STP on the Switch 2512 or Switch 2524 in a VLAN environment with redundant physical links, you can prevent blocked redundant links by using a port trunk. The following example shows how you can use a port trunk with 802.1Q (tagged) VLANs and STP without unnecessarily blocking any links or losing any bandwidth.

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