Beginning with Cisco IOS Release 12.2(33)SXI, you can specifically configure a spanning tree port as either an edge port, a network port, or a normal port. The port type determines the behavior of the port with respect to STP extensions.
* An edge port, which is connected to a Layer 2 host, can be either an access port or a trunk port.
* A network port is connected only to a Layer 2 switch or bridge.(If you mistakenly configure a port that is connected to a Layer 2 host as a spanning tree network port, the port will automatically move into the blocking state)
* The default spanning tree port type is normal, meaning only that its topology is not specified.
STP PortFast causes a Layer 2 LAN port configured as an access port to enter the forwarding state immediately, bypassing the listening and learning states. You can use PortFast on Layer 2 access ports connected to a single workstation or server to allow those devices to connect to the network immediately, instead of waiting for STP to converge. Interfaces connected to a single workstation or server should not receive bridge protocol data units (BPDUs). When configured for PortFast, a port is still running the spanning tree protocol. A PortFast enabled port can immediately transition to the blocking state if necessary (this could happen on receipt of a superior BPDU). PortFast can be enabled on trunk ports. PortFast can have an operational value that is different from the configured value.
You can configure PortFast feature on interface level or global configuration level. Here shows the interfaces configuration syntax for IOS 12.2(33)SXI code onwards.
6506(config)# interface g6/1 6506(config-if)#spanning-tree portfast ? disable Disable portfast for this interface edge Enable portfast edge on the interface network Enable portfast network on the interface ! 6506(config-if)#spanning-tree portfast edge ? trunk Enable portfast edge on the interface even in trunk mode ! 6506(config-if)#spanning-tree portfast disable ?
Here is the command syntax for global configurations of this feature. If a access port to be configured to PortFast then you have to use “spanning-tree portfast edge default” command in these IOS codes. In previous codes or any other type of switches (2960, 3750) it is simply “spanning-tree portfast default“. By doing this STP portfast enabled for all configured access ports on the switch.
6506(config)#spanning-tree portfast ? edge Spanning tree portfast edge options network Spanning tree portfast network options normal Spanning tree portfast normal options ! 6506(config)#spanning-tree portfast edge ? bpdufilter Enable portfast edge bdpu filter on this switch bpduguard Enable portfast edge bpdu guard on this switch default Enable portfast edge by default on all access ports ! 6506(config)#spanning-tree portfast network ? default Enable portfast network by default on all ports ! 6506(config)#spanning-tree portfast normal ? default Enable normal behavior by default on all ports
You can verify global or interfaces specific STP settings by using below commands.
6506#sh spanning-tree summary totals Switch is in rapid-pvst mode Root bridge for: VLAN0001, VLAN0160, VLAN0182, VLAN0199, VLAN0438, VLAN0585 VLAN0756, VLAN0783, VLAN0870, VLAN0888-VLAN0889, VLAN0990 EtherChannel misconfig guard is enabled Extended system ID is enabled Portfast Default is disabled Portfast Edge BPDU Guard Default is disabled Portfast Edge BPDU Filter Default is disabled Loopguard Default is disabled Platform PVST Simulation is enabled PVST Simulation Default is enabled but inactive in rapid-pvst mode Bridge Assurance is enabled UplinkFast is disabled BackboneFast is disabled Pathcost method used is short Name Blocking Listening Learning Forwarding STP Active ---------------------- -------- --------- -------- ---------- ---------- 13 vlans 0 0 0 13 13 6506#sh spanning-tree interface g6/2 detail Port 642 (GigabitEthernet6/2) of VLAN0001 is designated forwarding Port path cost 4, Port priority 128, Port Identifier 128.642. Designated root has priority 8193, address 00b0.c239.7000 Designated bridge has priority 8193, address 00b0.c239.7000 Designated port id is 128.642, designated path cost 0 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1 Link type is point-to-point by default, Peer is STP BPDU: sent 565, received 2 Port 642 (GigabitEthernet6/2) of VLAN0160 is designated forwarding Port path cost 4, Port priority 128, Port Identifier 128.642. Designated root has priority 8352, address 00b0.c239.7000 Designated bridge has priority 8352, address 00b0.c239.7000 Designated port id is 128.642, designated path cost 0 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1 Link type is point-to-point by default, Peer is STP BPDU: sent 565, received 2
In CCIE wireless lab perspective, WLC connected switch port normally configured as TRUNK. Since WLC is not participation STP, we can enable Portfast feature on these ports by using “spanning-tree portfast edge trunk” command.
Remember that “edge” keyword required for these configurations syntax on 6506 with 12.2 SXI onwards software codes.
Related Posts
1. Configuring STP in 12.2 SXI
2. Configuring STP-BPDU Guard & Filter
3. Configuring STP-Root Guard & Loop Guard
4. STP -
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