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TCC_2
Level 10
Level 10

Resolution

To reduce the delay, issue the set spantree portfast command on the switch port.

For example, to enable PortFast on port 3/2, issue the set spantree portfast 3/2 enable command.

This reduces Spanning Tree Protocol (STP) delay by about 30 seconds. By default, STP spends approximately 15 seconds listening and 15 seconds learning. This delay is not necessary when a single end station is directly connected to a switch port. Because a loop is not possible in that situation, there is no reason for spanning tree to spend 30 seconds checking for loops on that port.

The PortFast feature should never be used on switch ports that connect to other switches, hubs or routers. These connections may cause physical loops and it is very important that spanning tree go through the full initialization procedure. A spanning tree loop can bring the network down. If PortFast is turned on for a port that is part of a physical loop, it can cause a window of time where packets could possibly be continuously forwarded (and even multiply) in such a way that the network cannot recover.

 

These startup delays may also cause issues with clients other than Novell Internetwork Packet Exchange (IPX) workstations.

These are examples of other messages:

 

  • A Microsoft networking client may display No Domain Controllers Available.
  • DHCP may report No DHCP Servers Available.
  • An AppleTalk networking client may display Access to your AppleTalk network has been interrupted. To re-establish your connection, open and close the AppleTalk control panel.

    It is also possible that the AppleTalk client's chooser application either does not display a zone list or displays an incomplete zone list.

The same solution would apply in these instances as well.

For more information regarding startup delay issues and configuration, refer to Using PortFast and Other Commands to Fix Workstation Startup Connectivity Delays.

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