CCIE Routing & Switching v5 Workbook -
CCIE R&S v5 Advanced Technology Labs -
LAN Switching
STP UplinkFast
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 SW2 - SW4 to use the default STP priority for all VLANs.
Configure SW2 - SW4 with Spanning-Tree UplinkFast so that if their Root Port is lost,
they immediately select a new Root Port.
Verify this by shutting down the Root Port of SW2.
Configuration
SW2 - SW4:
default spanning-tree vlan 1-4094 priority
spanning-tree uplinkfast
Verification
The Cisco-proprietary UplinkFast feature is used to speed up convergence time
when the direct failure of the local Root Port occurs. This feature can be used only if
the switch runs legacy STP, 802.1D, because functionality is built in to RSTP,
802.1w. To ensure that the switch with UplinkFast configured does not become a
transit switch, its bridge priority will be automatically increased to 49152 and its
ports cost increased with 3000. UplinkFast cannot be enabled on a switch that has
its default STP priority modified.
Verify SW2’s STP bridge priority, port costs, and port states after configuring the
default STP priority but before configuring uplinkfast; for example, for VLAN 2:
SW2#show spanning-tree summary
Switch is in pvst mode
Root bridge for: none
Extended system ID
is enabled
Portfast Default
is disabled
PortFast BPDU Guard Default
is disabled
Portfast BPDU Filter Default is disabled
Loopguard Defaultis disabled
EtherChannel misconfig guard is enabledUplinkFastis disabled
BackboneFastis disabled
Configured Pathcost method used is short
NameBlocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
VLAN000110034
VLAN000210034
VLAN000510034
VLAN000710034
VLAN000810034
VLAN000910034
VLAN001010034
VLAN002210034
VLAN004310034
VLAN005810034
VLAN006710034
VLAN007910034
VLAN014610034
---------------------- -------- --------- -------- ---------- ----------
13 vlans13003952
!
!SW2#show spanning-tree vlan 2
VLAN0002
Spanning tree enabled protocol ieee
Root IDPriority4098
Address
0013.605f.f000
Cost
19
Port
25 (FastEthernet0/23)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority32770 (priority 32768 sys-id-ext 2)
Address000a.b832.3a80
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 15 sec
InterfaceRole Sts CostPrio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/19Desg FWD 19
128.21 P2p
Fa0/20Desg FWD 19
128.22 P2p
Fa0/23Root FWD 19
128.25 P2p
Fa0/24Altn BLK 19
128.26 P2p
Enable STP event debugging only for VLAN 2, shut down the Root Port that is
FastEthernet0/23, and notice that FastEhernet0/24 transitions to listening and
learning before forwarding, so it is not automatically selected as the new Root Port.
SW2#debug spanning-tree events
Spanning Tree event debugging is on
!SW2#debug condition vlan 2
Condition 1 set
!SW2#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
SW2(config)#service timestamps debug datetime msec
SW2(config)#interface fastEthernet0/23
SW2(config-if)#shutdown
!
!
*Mar 1 00:19:07.980: STP: VLAN0002 new root port Fa0/24, cost 19
*Mar 1 00:19:07.980: STP: VLAN0002 Fa0/24 -> listening
*Mar 1 00:19:07.980: STP[2]: Generating TC trap for port FastEthernet0/23
*Mar 1 00:19:09.985: STP: VLAN0002 sent Topology Change Notice on Fa0/24
*Mar 1 00:19:22.988: STP: VLAN0002 Fa0/24 -> learning
*Mar 1 00:19:37.995: STP[2]: Generating TC trap for port FastEthernet0/24
*Mar 1 00:19:37.995: STP: VLAN0002 sent Topology Change Notice on Fa0/24
*Mar 1 00:19:37.995: STP: VLAN0002 Fa0/24 -> forwarding
!
!SW2#show spanning-tree vlan 2
VLAN0002
Spanning tree enabled protocol ieee
Root IDPriority
4098
Address
0013.605f.f000
Cost
19
Port
25 (FastEthernet0/23)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority32770 (priority 32768 sys-id-ext 2)
Address000a.b832.3a80
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 15 sec
InterfaceRole Sts CostPrio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/19Desg FWD 19
128.21 P2p
Fa0/20Desg FWD 19
128.22 P2pFa0/24Root FWD 19128.26 P2p
Configure uplinkfast and notice how SW2’s STP bridge priority and port costs have
been increased; for example, for VLAN 2:
SW2#show spanning-tree vlan 2
VLAN0002
Spanning tree enabled protocol ieee
Root IDPriority
4098
Address
0013.605f.f000
Cost
3019
Port
25 (FastEthernet0/23)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority49154 (priority 49152 sys-id-ext 2)
Address000a.b832.3a80
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Uplinkfast enabled
InterfaceRole Sts CostPrio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/19Desg FWD 3019
128.21 P2p
Fa0/20Desg FWD 3019
128.22 P2p
Fa0/23Root FWD 3019
128.25 P2p
Fa0/24Altn BLK 3019
128.26 P2p
Enable STP event debugging only for VLAN 2, shut down the Root Port that is
FastEthernet0/23, and notice that FastEhernet0/24 transitions directly to forwarding,
so it is automatically selected the new Root Port.
SW2#debug spanning-tree events
Spanning Tree event debugging is on
!SW2#debug condition vlan 2
Condition 1 set
!SW2#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
SW2(config)#service timestamps debug datetime msec
SW2(config)#interface fastEthernet0/23
SW2(config-if)#shutdown
!
!%SPANTREE_FAST-7-PORT_FWD_UPLINK: VLAN0001 FastEthernet0/24 moved to Forwarding (UplinkFast).
*Mar 1 01:09:03.619: STP: VLAN0002 new root port Fa0/24, cost 3019
*Mar 1 01:09:03.619: STP[2]: Generating TC trap for port FastEthernet0/24
*Mar 1 01:09:03.619: STP[2]: Generating TC trap for port FastEthernet0/23
*Mar 1 01:09:05.624: STP: VLAN0002 sent Topology Change Notice on Fa0/24
!
!SW2#show spanning-tree vlan 2
VLAN0002
Spanning tree enabled protocol ieee
Root IDPriority
4098
Address
0013.605f.f000
Cost
3019
Port
26 (FastEthernet0/24)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority49154 (priority 49152 sys-id-ext 2)
Address000a.b832.3a80
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Uplinkfast enabled
InterfaceRole Sts CostPrio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/19Desg FWD 3019
128.21 P2p
Fa0/20Desg FWD 3019
128.22 P2p Fa0/24Root FWD 3019128.26 P2p
Verify that UplinkFast is enabled, and based on statistics it has been used when the
Root Port has changed. The CAM table was flooded out the new Root Port to
expedite the learning phase of upstream neighbors.
SW2#show spanning-tree summary
Switch is in pvst mode
Root bridge for: none
Extended system ID
is enabled
Portfast Default
is disabled
PortFast BPDU Guard Default
is disabled
Portfast BPDU Filter Default is disabled
Loopguard Defaultis disabled
EtherChannel misconfig guard is enabledUplinkFastis enabled
BackboneFastis disabled
Configured Pathcost method used is short
NameBlocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
VLAN000100033
VLAN000200033
VLAN000500033
VLAN000700033
VLAN000800033
VLAN000900033
VLAN001000033
VLAN002200033
VLAN004300033
VLAN005800033
VLAN006700033
VLAN007900033
VLAN014600033
---------------------- -------- --------- -------- ---------- ----------
13 vlans0003939
Station update rate set to 150 packets/sec.
UplinkFast statistics
-----------------------Number of transitions via uplinkFast (all VLANs): 26
Number of proxy multicast addresses transmitted (all VLANs) : 84