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vmproteau
Enthusiast
Enthusiast

Network physical switch port configuration “spanning-tree portfast trunk”

Most of the environments I've supported have used Cisco switches and I've always requested “spanning-tree portfast trunk”. The environment I support now use chassis switching from a different vendor. I was wondering if that vendors equivilant command would still be considered a best practice on these switches? Are there any additional or alternate trunk port configuration settings recommended for these switches?

  • PowerConnect M8024
  • Dell Force10 MXL 10/40GbE chassis switches
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admin
Immortal
Immortal

STP is used to accomplish a loop-free environment. Every time a port state goes up, STP calculation occurs. As the result of the calculation, the switch ports are either set to a forwarding or blocking state to prevent a traffic loop.

STP topology convergence has four states:

  • Blocking
  • Listening
  • Learning
  • Forwarding

When STP convergence is initiated it forces all of the physical switches in the STP domain to dump their forwarding tables and relearn the STP topology and all MAC addresses. This process can take between 30-50 seconds. During this time, no user data passes through the port. Some user applications can time out during this period. Connectivity is restored when the STP domain completes this convergence.  To prevent the 30-50 second loss of connectivity during STP convergence, perform one of these options: 

  • Set STP to Portfast on all switch ports that are connected to network adapters on an ESXi/ESX host.
  • Disable STP.

  • To set STP to Portfast on all switch ports that are connected to network adapters on an ESXi/ESX host

    Portfast allows the ports to immediately be set back to the forwarding state and prevents the link state changes that occur on ESX/ESXi hosts from affecting the STP topology.  Setting STP to Portfast prevents the 30-50 second loss of network connectivity.

    The command to set STP to Portfast depends on the model of the switch.
    As the command will be different from model to model and vendor to vendor, contact your physical switch vendor for more detailed information on how to configure the same.

    For example:

    To set STP to Portfast on a switch, run the below command based on the switch model:

    • CISCO-IOS

      spanning-tree portfast (for an access port)
      spanning-tree portfast trunk (for a trunk port)
    • NX-IOS

      spanning-tree port type edge (for an access port)
      s
      panning-tree port type edge trunk (for a trunk port)

    • To set STP to Portfast on a Dell switch, run the command:

      spanning-tree portfast
    • HP switches use a feature called admin-edge-port, which works the same way as Portfast or RSTP. To enable admin-edge-port, run the command:

      spanning-tree port-list admin-edge-port
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