CCIE Routing & Switching v5 Workbook -
CCIE R&S v5 Advanced Technology Labs -
LAN Switching
STP PortFast
A Note On Section Initial Configuration Files: You must load the
initial configuration files for the section, named LAN Switching Initial
Spanning Tree, which can be found in
. Reference the Virtual Routers &
Physical Switches Diagram to complete this task.
Task
Configure Spanning-Tree PortFast on SW1 so that port FastEthernet0/1 does not
have to wait for the Spanning-Tree listening and learning phases to begin forwarding.
Configure FastEthernet0/1 on SW1 as a trunk port using 802.1q
encapsulation.
Do not use any global Spanning-Tree commands to accomplish this.
Configuration
SW1:
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
spanning-tree portfast trunk
Verification
Portfast is used to override the listening and learning phases of Spanning-Tree, also
called the forwarding delay, and transition immediately to forwarding. Note that in
this example, we are enabling PortFast on a trunk port, which requires the additional
trunk
keyword attached to the
spanning-tree portfast
command. This is useful
when you have a trunk port connected to a server, such as a hypervisor, that is
running multiple virtual machines and using a virtual switch with multiple VLANs.
Although trunking can be used between switches, trunking can also be used to
connect to single devices that can tag traffic with 802.1q. Another example would be
a VOIP phone with a PC connected to it that tags voice traffic with one VLAN but
data traffic from the PC with another VLAN; this was actually the voice
implementation before the voice VLAN functionality, also known as the auxiliary
VLAN, was added to the switch.
SW1#show spanning-tree interface fastethernet0/1 portfast
VLAN0001
enabled
VLAN0005
enabled
VLAN0007
enabled
VLAN0008
enabled
VLAN0009
enabled
VLAN0010
enabled
VLAN0022
enabled
VLAN0043
enabled
VLAN0058
enabled
VLAN0067
enabled
VLAN0079
enabled
VLAN0146
enabled
!
!SW1#show spanning-tree interface fastEthernet0/1 detail
Port 3 (FastEthernet0/1) of VLAN0001 is designated forwarding
Port path cost 19, Port priority 128, Port Identifier 128.3.
Designated root has priority 4097, address 0013.605f.f000
Designated bridge has priority 4097, address 0013.605f.f000
Designated port id is 128.3, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
The port is in the portfast mode by portfast trunk configuration
Link type is point-to-point by default
BPDU: sent 686, received 0
Port 3 (FastEthernet0/1) of VLAN0005 is designated forwarding
Port path cost 19, Port priority 128, Port Identifier 128.3.
Designated root has priority 4101, address 0013.605f.f000
Designated bridge has priority 4101, address 0013.605f.f000
Designated port id is 128.3, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
The port is in the portfast mode by portfast trunk configuration
Link type is point-to-point by default
BPDU: sent 686, received 0
<output omitted>
!SW1#debug spanning-tree event
Spanning Tree event debugging is on
!SW1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
SW1(config)#service timestamps debug datetime msec
SW1(config)#logging console 7
SW1(config)#interface FastEthernet0/1
SW1(config-if)#shutdown
!
*Mar 3 05:15:45.999: STP: VLAN0001 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0005 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0007 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0008 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0009 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0010 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0022 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0043 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0058 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0067 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0079 we are the spanning tree root
*Mar 3 05:15:45.999: STP: VLAN0146 we are the spanning tree root
%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administratively down
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down
When interface FastEthernet0/1 is shut down and subsequently brought back up, it
immediately transitions to the forwarding state for all VLANs allowed on the trunk.
SW1(config-if)#no shutdown
!
*Mar 3 22:52:28.732: set portid: VLAN0005 Fa0/1: new port id 8003*Mar 3 22:52:28.732:
STP: VLAN0005 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.732: set portid: VLAN0007 Fa0/1: new port id 8003*Mar 3 22:52:28.732:
STP: VLAN0007 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0008 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0008 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0009 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0009 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0010 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0010 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0022 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0022 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0043 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0043 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0058 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0058 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0067 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0067 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0079 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0079 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.740: set portid: VLAN0146 Fa0/1: new port id 8003*Mar 3 22:52:28.740:
STP: VLAN0146 Fa0/1 ->jump to forwarding from blocking
*Mar 3 22:52:28.749: set portid: VLAN0001 Fa0/1: new port id 8003*Mar 3 22:52:28.749:
STP: VLAN0001 Fa0/1 ->jump to forwarding from blocking
!
%LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up