Spanning Tree Protocol
Lab 3-2: Advanced Spanning Tree Protocol (802.1D)
Figure 3-2 illustrates the topology that will be used in the following tasks.
F0/20
Figure 3-2 Complete 802.1D Lab Topology F0/19–20
Figure 3-3 Advanced Spanning Tree Protocol (802.1D)
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Task 1
Shut down all ports on all switches and configure the hostnames of these switches based on Figure 3-3.
On All Switches:
SWx(config)# interface range FastEthernet0/1 - 24 SWx(config-if-range)# shut
Let’s verify the configuration:
On All Switches:
SWx# show interface status
Port Name Status Vlan Duplex Speed Type Fa0/1 disabled 1 auto auto 10/100BaseTX Fa0/2 disabled 1 auto auto 10/100BaseTX Fa0/3 disabled 1 auto auto 10/100BaseTX Fa0/4 disabled 1 auto auto 10/100BaseTX Fa0/5 disabled 1 auto auto 10/100BaseTX Fa0/6 disabled 1 auto auto 10/100BaseTX Fa0/7 disabled 1 auto auto 10/100BaseTX Fa0/8 disabled 1 auto auto 10/100BaseTX Fa0/9 disabled 1 auto auto 10/100BaseTX Fa0/10 disabled 1 auto auto 10/100BaseTX Fa0/11 disabled 1 auto auto 10/100BaseTX Fa0/12 disabled 1 auto auto 10/100BaseTX Fa0/13 disabled 1 auto auto 10/100BaseTX Fa0/14 disabled 1 auto auto 10/100BaseTX Fa0/15 disabled 1 auto auto 10/100BaseTX Fa0/16 disabled 1 auto auto 10/100BaseTX Fa0/17 disabled 1 auto auto 10/100BaseTX Fa0/18 disabled 1 auto auto 10/100BaseTX Fa0/19 disabled 1 auto auto 10/100BaseTX Fa0/20 disabled 1 auto auto 10/100BaseTX Fa0/21 disabled 1 auto auto 10/100BaseTX Fa0/22 disabled 1 auto auto 10/100BaseTX Fa0/23 disabled 1 auto auto 10/100BaseTX Fa0/24 disabled 1 auto auto 10/100BaseTX
On SW1:
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On SW2:
SW2(config)# hostname SW2
On SW3:
SW3(config)# hostname SW3
On SW4:
SW4(config)# hostname SW4
Task 2
Configure ports F0/19–20 connecting SW1 to SW2 and SW3 to SW4 as trunk ports. You should use an industry-standard protocol to accomplish this task. These ports should never become an access port through negotiation.
On SW1, SW2, SW3 and SW4:
SWx(config)# interface range FastEthernet0/19-20
SWx(config-if-range)# switchport trunk encapsulation dot1q SWx(config-if-range)# switchport mode trunk
SWx(config-if-range)# no shut
Let’s verify the configuration:
On SW1:
SW1# show interface trunk | include trunking
Fa0/19 on 802.1q trunking 1 Fa0/20 on 802.1q trunking 1
On SW2:
SW2# show interface trunk | include trunking
Fa0/19 on 802.1q trunking 1 Fa0/20 on 802.1q trunking 1
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On SW3:
SW3# show interface trunk | inc trunking
Fa0/19 on 802.1q trunking 1 Fa0/20 on 802.1q trunking 1
On SW4:
SW4# show interface trunk | include trunking
Fa0/19 on 802.1q trunking 1 Fa0/20 on 802.1q trunking 1
Task 3
Configure ports F0/21–22 connecting SW2 to SW4 and SW1 to SW3 as trunk ports. You should use an industry-standard protocol to accomplish this task. These ports should never become an access port through negotiation.
On SW1, SW2, SW3 and SW4:
SWx(config)# interface range FastEthernet0/21-22
SWx(config-if-range)# switchport trunk encapsulation dot1q SWx(config-if-range)# switchport mode trunk
SWx(config-if-range)# no shut
Let’s verify the configuration:
On SW1:
SW1# show interface trunk | include trunking
Fa0/19 on 802.1q trunking 1 Fa0/20 on 802.1q trunking 1 Fa0/21 on 802.1q trunking 1 Fa0/22 on 802.1q trunking 1
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On SW2:
SW2# show interface trunk | include trunking
Fa0/19 on 802.1q trunking 1 Fa0/20 on 802.1q trunking 1
Fa0/21 on 802.1q trunking 1 Fa0/22 on 802.1q trunking 1
On SW3
SW3# show interface trunk | include trunking
Fa0/19 on 802.1q trunking 1 Fa0/20 on 802.1q trunking 1 Fa0/21 on 802.1q trunking 1 Fa0/22 on 802.1q trunking 1
On SW4
SW4# show interface trunk | include trunking
Fa0/19 on 802.1q trunking 1 Fa0/20 on 802.1q trunking 1 Fa0/21 on 802.1q trunking 1 Fa0/22 on 802.1q trunking 1
Task 4
These switches should be configured in a VLAN Trunking Protocol (VTP) domain called
“CCIE”:
On SW1:
SW1(config)# vtp domain CCIE
This configuration will be propagated via VTP to the other switches.
ptg19878261 Let’s verify the configuration:
On All Switches:
SWx# show vtp status | include VTP Domain Name
VTP Domain Name : CCIE
Note The domain name is propagated by VTP messages when the trunk is established between the switches.
Task 5
Create the VLANs 100, 200, 300, and 400 and ensure they are propagated to all four switches:
On SW1:
SW1(config)# vlan 100,200,300,400
SW1(config-vlan)# exit You must "exit" for the VLANs to be propagated.
Let’s verify the configuration:
On SW1:
SW1# show vlan brief | include VLAN
VLAN Name Status Ports 100 VLAN0100 active
200 VLAN0200 active 300 VLAN0300 active 400 VLAN0400 active
On SW2:
SW2# show vlan brief | include VLAN
VLAN Name Status Ports 100 VLAN0100 active
200 VLAN0200 active 300 VLAN0300 active
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On SW3:
SW3# show vlan brief | include VLAN
VLAN Name Status Ports
100 VLAN0100 active 200 VLAN0200 active 300 VLAN0300 active 400 VLAN0400 active
On SW4:
SW4# show vlan brief | include VLAN
VLAN Name Status Ports 100 VLAN0100 active
200 VLAN0200 active 300 VLAN0300 active 400 VLAN0400 active
Task 6
Ensure that SW1 is the root bridge for VLAN 100, SW2 is the root bridge for VLAN 200, SW3 is the root bridge for VLAN 300, and SW4 is the root bridge for VLAN 400.
You should use a macro to accomplish this task.
On SW1:
SW1(config)# spanning-tree vlan 100 root primary
On SW2:
SW2(config)# spanning-tree vlan 200 root primary
On SW3:
SW3(config)# spanning-tree vlan 300 root primary
On SW4:
ptg19878261 Let’s verify the configuration:
On SW1:
SW1# show spanning-tree vlan 100
VLAN0100
Spanning tree enabled protocol ieee Root ID Priority 24676
Address 0012.7f40.9380 This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24676 (priority 24576 sys-id-ext 100) Address 0012.7f40.9380
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 15
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Desg FWD 19 128.21 P2p
Fa0/20 Desg FWD 19 128.22 P2p Fa0/21 Desg FWD 19 128.23 P2p Fa0/22 Desg FWD 19 128.24 P2p
Note Because SW1 is the root bridge for VLAN 100, all of the trunk interfaces are desig-nated ports.
SW1# show version | include Base
Base ethernet MAC Address : 00:12:7F:40:93:80
On SW2:
SW2# show spanning-tree vlan 200
VLAN0200
Spanning tree enabled protocol ieee Root ID Priority 24776
Address 001d.e5d6.0000 This bridge is the root
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Bridge ID Priority 24776 (priority 24576 sys-id-ext 200) Address 001d.e5d6.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Desg FWD 19 128.21 P2p
Fa0/20 Desg FWD 19 128.22 P2p Fa0/21 Desg FWD 19 128.23 P2p Fa0/22 Desg FWD 19 128.24 P2p
SW2# show version | include Base
Base ethernet MAC Address : 00:1D:E5:D6:00:00
On SW3:
SW3# show spanning-tree vlan 300
VLAN0300
Spanning tree enabled protocol ieee Root ID Priority 24876
Address 000c.858b.7a00 This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24876 (priority 24576 sys-id-ext 300) Address 000c.858b.7a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 15
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Desg FWD 19 128.19 P2p
Fa0/20 Desg FWD 19 128.20 P2p Fa0/21 Desg FWD 19 128.21 P2p Fa0/22 Desg FWD 19 128.22 P2p
SW3# show version | include Base
Base ethernet MAC Address: 00:0C:85:8B:7A:00
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On SW4:
SW4# show spanning-tree vlan 400
VLAN0400
Spanning tree enabled protocol ieee Root ID Priority 24976
Address 000c.302d.9980 This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24976 (priority 24576 sys-id-ext 400) Address 000c.302d.9980
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Desg FWD 19 128.19 P2p
Fa0/20 Desg FWD 19 128.20 P2p Fa0/21 Desg FWD 19 128.21 P2p Fa0/22 Desg FWD 19 128.22 P2p
SW4# show version | include Base
Base ethernet MAC Address: 00:0C:30:2D:99:80
Task 7
Implement the following policies:
■ VLAN 100 should never traverse SW4. This switch should not receive/send traffic for this VLAN.
■ VLAN 200 should never traverse SW3. This switch should not receive/send traffic for this VLAN.
■ VLAN 300 should never traverse SW2. This switch should not receive/send traffic for this VLAN.
■ VLAN 400 should never traverse SW1. This switch should not receive/send traffic for this VLAN.
ptg19878261 Let’s configure the first policy:
On SW2:
SW2(config)# interface range FastEthernet0/21-22
SW2(config-if-range)# switchport trunk allowed vlan except 100
On SW3:
SW3(config)# interface range FastEthernet0/19-20
SW3(config-if-range)# switchport trunk allowed vlan except 100
On SW4:
SW4(config)# interface range FastEthernet0/19-20 , FastEthernet0/21-22 SW4(config-if-range)# switchport trunk allowed vlan except 100
Now let’s verify the configuration:
On SW2:
SW2# show interface trunk | exclude trunking|200|300|domain|pruned|Enc
Port Vlans allowed on trunk Fa0/19 1-4094
Fa0/20 1-4094
Fa0/21 1-99,101-4094 The traffic for VLAN 100 is NOT Fa0/22 1-99,101-4094 allowed on these trunk links.
On SW3:
SW3# show interface trunk | exclude trunking|200|300|domain|pruned|Enc
Port Vlans allowed on trunk
Fa0/19 1-99,101-4094 The traffic for VLAN 100 is NOT Fa0/20 1-99,101-4094 allowed on these trunk links.
Fa0/21 1-4094 Fa0/22 1-4094
ptg19878261 Now let’s configure the second policy:
Note Make sure the first policy in this task is not overridden by the next policy.
On SW1:
SW1(config)# interface range FastEthernet0/21-22
SW1(config-if-range)# switchport trunk allowed vlan except 200
On SW4:
SW4(config)# interface range FastEthernet0/19-20
SW4(config-if-range)# switchport trunk allowed vlan except 100,200
On SW3:
SW3(config)# interface range FastEthernet0/19-20
SW3(config-if-range)# switchport trunk allowed vlan except 100,200
SW3(config)# interface range FastEthernet0/21-22
SW3(config-if-range)# switchport trunk allowed vlan except 200
Let’s verify the configuration:
On SW1:
SW1# show interface trunk | exclude trunking|200|300|100|pruned|domain|Enc
Port Vlans allowed on trunk Fa0/19 1-4094
Fa0/20 1-4094 The traffic for VLAN 200 is NOT Fa0/21 1-199,201-4094 allowed on these trunk links.
On SW4:
SW4# show interface trunk | exclude trunking|200|300|pruned|domain|Enc
Port Vlans allowed on trunk Fa0/19 1-99,101-4094
Fa0/20 1-99,101-4094 The traffic for VLAN 100 is NOT Fa0/21 1-99,101-4094 allowed on these trunk links.
Fa0/22 1-99,101-4094
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On SW4:
SW4# show interface trunk | exclude trunking|200|300|400|pruned|domain|Enc
Port Vlans allowed on trunk
Fa0/19 1-99,101-199,201-4094 The traffic for VLANs 100 or 200 Fa0/20 1-99,101-199,201-4094 is NOT allowed on these trunk links.
Fa0/21 1-99,101-4094 The traffic for VLAN 100 is NOT Fa0/22 1-99,101-4094 allowed on these trunk links.
On SW3:
SW3# show interface trunk | exclude trunking|200|300|pruned|domain|Enc
Port Vlans allowed on trunk
Fa0/19 1-99,101-199,201-4094 The traffic for VLANs 100 and 200 Fa0/20 1-99,101-199,201-4094 is NOT allowed on these trunk links.
Fa0/21 1-199,201-4094 The traffic for VLAN 200 is Fa0/22 1-199,201-4094 NOT allowed on these trunk links.
Now let’s configure the third policy:
On SW2:
SW2(config-if-range)# interface range FastEthernet0/21-22
SW2(config-if-range)# switchport trunk allowed vlan except 100,300
SW2(config-if-range)# interface range FastEthernet0/19-20 SW2(config-if-range)# switchport trunk allowed vlan except 300
On SW4:
SW4(config)# interface range FastEthernet0/21-22
SW4(config-if-range)# switchport trunk allowed vlan except 100,300
On SW1:
SW1(config)# interface range FastEthernet0/19-20
SW1(config-if-range)# switchport trunk allowed vlan except 300
ptg19878261 Now you need to verify the configuration:
On SW2:
SW2# show interface trunk | exclude trunking|200|400|pruned|domain|Enc
Port Vlans allowed on trunk
Fa0/19 1-299,301-4094 The traffic for VLAN 300 is NOT Fa0/20 1-299,301-4094 allowed on these trunk links.
Fa0/21 1-99,101-299,301-4094 The traffic for VLANs 100 or 300 is Fa0/22 1-99,101-299,301-4094 NOT allowed on these trunk links.
On SW4:
SW4# show interface trunk | exclude trunking|200|300|400|pruned|domain|Enc
Port Vlans allowed on trunk
Fa0/19 1-99,101-199,201-4094 The traffic for VLANs 100 or 200 is Fa0/20 1-99,101-199,201-4094 NOT allowed on these trunk links.
Fa0/21 1-99,101-299,301-4094 The traffic for VLANs 100 or 300 Fa0/22 1-99,101-299,301-4094 is NOT allowed on these trunk links.
On SW1:
SW1# show interface trunk | exclude trunking|200|300|100|pruned|domain|Enc
Port Vlans allowed on trunk
Fa0/19 1-299,301-4094 The traffic for VLAN 300 is NOT Fa0/20 1-299,301-4094 allowed on this trunk link.
Fa0/21 1-199,201-4094 The traffic for VLAN 200 is NOT Fa0/22 1-199,201-4094 allowed on this trunk link.
Finally, let’s configure the fourth policy:
On SW1:
SW1(config)# interface range FastEthernet0/19-20
SW1(config-if-range)# switchport trunk allowed vlan except 300,400
SW1(config)# interface range FastEthernet0/21-22
SW1(config-if-range)# switchport trunk allowed vlan except 200,400
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On SW2:
SW2(config)# interface range FastEthernet0/19-20
SW2(config-if-range)# switchport trunk allowed vlan except 300,400
On SW3:
SW3(config)# interface range FastEthernet0/21-22
SW3(config-if-range)# switchport trunk allowed vlan except 200,400
Let’s verify the configuration:
On SW1:
SW1# show interface trunk | exclude trunking|200|300|100|pruned|domain|Enc
Port Vlans allowed on trunk
Fa0/19 1-299,301-399,401-4094 The traffic for VLANs 300 or 400 Fa0/20 1-299,301-399,401-4094 is NOT allowed on these trunk links Fa0/21 1-199,201-399,401-4094 The traffic for VLANs 200 or 400 Fa0/22 1-199,201-399,401-4094 is NOT allowed on these trunk links.
On SW2:
SW2# show interface trunk | exclude trunking|100|200|300|pruned|domain|Enc
Port Vlans allowed on trunk
Fa0/19 1-299,301-399,401-4094 The traffic for VLANs 300 or 400 Fa0/20 1-299,301-399,401-4094 is NOT allowed on these trunk links.
Fa0/21 1-99,101-299,301-4094 The traffic for VLANs 100 or 300 is Fa0/22 1-99,101-299,301-4094 NOT allowed on these trunk links.
On SW3:
SW3# show interface trunk | exclude trunking|200|300|pruned|domain|Enc
Port Vlans allowed on trunk
Fa0/19 1-99,101-199,201-4094 The traffic for VLANs 100 or 200 is Fa0/20 1-99,101-199,201-4094 NOT allowed on these trunk links.
Fa0/21 1-199,201-399,401-4094 The traffic for VLANs 200 or 400 is Fa0/22 1-199,201-399,401-4094 NOT allowed on these trunk links.
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Task 8
Configure SW1 such that it’s the root bridge for VLAN 500. If this switch goes down, SW2 should become the root bridge for this VLAN. Do not override any of the previous tasks to accomplish this one.
On SW1:
SW1(config)# spanning-tree vlan 500 root primary
SW1# debug spanning-tree events Spanning Tree event debugging is on
SW1(config)# vlan 500
Note When you’re creating a VLAN in global config mode, the VLAN is not created and propagated unless you exit out of VLAN configuration mode:
SW1(config-vlan)# exit
Once you have exited out of VLAN configuration mode, you should see the following console messages:
setting bridge id (which=3) prio 25076 prio cfg 24576 sysid 500 (on) id
61F4.0012.7f40.9380
set portid: VLAN0500 Fa0/19: new port id 8015 STP: VLAN0500 Fa0/19 -> listening
set portid: VLAN0500 Fa0/20: new port id 8016 STP: VLAN0500 Fa0/20 -> listening
set portid: VLAN0500 Fa0/21: new port id 8017 STP: VLAN0500 Fa0/21 -> listening
STP: VLAN0500 heard root 33268-000c.858b.7a00 on Fa0/21 STP: VLAN0500 heard root 33268-000c.858b.7a00 on Fa0/22 STP: VLAN0500 heard root 33268-001d.e5d6.0000 on Fa0/19 STP: VLAN0500 heard root 33268-001d.e5d6.0000 on Fa0/20
STP: VLAN0500 Fa0/19 -> learning
STP: VLAN0500 Fa0/20 -> learning
ptg19878261 Let’s disable the debug:
On SW1:
SW1# undebug all
On SW2:
SW2(config)# spanning-tree vlan 500 root secondary
Now let’s verify the configuration:
On SW2:
SW2# show spanning-tree vlan 500 | exclude Interface|Fa0
VLAN0500
Spanning tree enabled protocol ieee Root ID Priority 25076
Address 0012.7f40.9380 Cost 19
Port 21 (FastEthernet0/19)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 29172 (priority 28672 sys-id-ext 500) Address 001d.e5d6.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300
--- ---- --- --- --- ---
Note: SW1 is the root.
On SW1:
SW1# show version | include Base
Base ethernet MAC Address : 00:12:7F:40:93:80 STP: VLAN0500 Fa0/21 -> learning
STP: VLAN0500 Fa0/22 -> learning
STP: VLAN0500 Fa0/19 -> forwarding STP: VLAN0500 Fa0/20 -> forwarding STP: VLAN0500 Fa0/21 -> forwarding STP: VLAN0500 Fa0/22 -> forwarding
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Task 9
Create VLAN 500 and ensure the traffic from SW2 for VLAN 500 takes the following path:
SW2 → SW4 → SW3 → SW1
SW2 should use port F0/19 or F0/20 only if the path through SW4 → SW3 → SW1 is not possible due to a link failure.
On SW2:
SW2# show spanning-tree vlan 500
VLAN0500
Spanning tree enabled protocol ieee Root ID Priority 25076
Address 0012.7f40.9380 Cost 19
Port 21 (FastEthernet0/19)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 29172 (priority 28672 sys-id-ext 500) Address 001d.e5d6.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Root FWD 19 128.21 P2p
Fa0/20 Altn BLK 19 128.22 P2p Fa0/21 Desg FWD 19 128.23 P2p Fa0/22 Desg FWD 19 128.24 P2p
Note SW2 is taking port F0/19 to get to the root bridge for VLAN 500, and its root cost is 19, which is the cost of a 100-Mbps link. If these ports (F0/19 and F0/20) are shut down, you should see the cost of the local switch (SW2) to the root bridge, which should be 57. The fol-lowing reveals the cumulative cost of the local switch to the root bridge for VLAN 500.
Let’s add the total cost:
The cost of the link from SW2 → SW4 is 19.
The cost of the link from SW4 → SW3 is 19.
The cost of the link from SW3 → SW1 is 19.
ptg19878261 Let’s verify this information:
On SW2:
SW2(config)# interface range FastEthernet0/19-20 SW2(config-if-range)# shut
Let’s verify the new cost:
SW2# show spanning-tree vlan 500
VLAN0500
Spanning tree enabled protocol ieee Root ID Priority 25076
Address 0012.7f40.9380 Cost 57
Port 23 (FastEthernet0/21)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 29172 (priority 28672 sys-id-ext 500) Address 001d.e5d6.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/21 Root FWD 19 128.23 P2p
Fa0/22 Altn BLK 19 128.24 P2p
Note VLAN 500 is taking port F0/21 toward the root bridge through SW4. If this is traced all the way back to SW1, you will see the path from SW2’s perspective.
SW2 → SW4 → SW3 → SW1
To configure this task, you should issue no shutdown on ports F0/19–20 first:
On SW2:
SW2(config)# interface range FastEthernet0/19-20 SW2(config-if-range)# no shut
SW2(config-if-range)# spanning-tree vlan 500 cost 58
ptg19878261 Note The preceding command sets the cost through ports F0/19–20 higher than 57.
Therefore, traffic from SW2 for VLAN 500 will have two paths:
■ Primary: SW2 → SW4 → SW3 → SW1
■ Backup: SW2 → SW1
Let’s verify the configuration:
On SW2:
SW2# show spanning-tree vlan 500
VLAN0500
Spanning tree enabled protocol ieee Root ID Priority 25076
Address 0012.7f40.9380 Cost 57
Port 23 (FastEthernet0/21)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 29172 (priority 28672 sys-id-ext 500) Address 001d.e5d6.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Altn BLK 58 128.21 P2p
Fa0/20 Altn BLK 58 128.22 P2p Fa0/21 Root FWD 19 128.23 P2p Fa0/22 Altn BLK 19 128.24 P2p
On SW2:
SW2(config)# interface range FastEthernet0/21-22 SW2(config-if-range)# shut
ptg19878261 You should wait 30 seconds before performing the following show command:
SW2# show spanning-tree vlan 500
VLAN0500
Spanning tree enabled protocol ieee Root ID Priority 25076
Address 0012.7f40.9380 Cost 58
Port 21 (FastEthernet0/19)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 29172 (priority 28672 sys-id-ext 500) Address 001d.e5d6.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Root FWD 58 128.21 P2p
Fa0/20 Altn BLK 58 128.22 P2p
On SW2:
SW2(config)# interface range FastEthernet0/21-22 SW2(config-if-range)# no shut
Task 10
Create VLAN 600 and configure SW3 as the root bridge for this VLAN. This switch should be configured such that traffic for VLAN 600 uses the following ports:
■ F0/22 from SW1
■ F0/20 from SW4
On SW-3:
SW3(config)# vlan 600 SW3(config-vlan)# exit
SW3(config)# spanning-tree vlan 600 root primary
ptg19878261 Let’s look at the existing path from SW1 and SW4:
On SW1:
SW1# show spanning-tree vlan 600
VLAN0600
Spanning tree enabled protocol ieee Root ID Priority 25176
Address 000c.858b.7a00 Cost 19
Port 23 (FastEthernet0/21)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 33368 (priority 32768 sys-id-ext 600) Address 0012.7f40.9380
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 15
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- ---
Fa0/19 Desg FWD 19 128.21 P2p Fa0/20 Desg FWD 19 128.22 P2p Fa0/21 Root FWD 19 128.23 P2p Fa0/22 Altn BLK 19 128.24 P2p
On SW4:
SW4# show spanning-tree vlan 600
VLAN0600
Spanning tree enabled protocol ieee Root ID Priority 25176
Address 000c.858b.7a00 Cost 19
Port 19 (FastEthernet0/19)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 33368 (priority 32768 sys-id-ext 600) Address 000c.302d.9980
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300
ptg19878261 Now we can configure the task:
On SW3:
SW-3(config)# interface range FastEthernet0/20 , FastEthernet0/22 SW-3(config-if)# spanning-tree vlan 600 port-priority 0
By default, the port priority of all interfaces for all VLANs is set to 128. Remember, the lower cost has higher preference. If the port priority of the ports connecting this switch to SW1 and SW4 (F0/20 and F0/22 for SW4 and SW1, respectively) is reduced, these ports will be the preferred ports for connecting to the root bridge, which in this case is SW4.
Let’s verify the configuration:
On SW3:
SW3# show spanning-tree vlan 600 | begin Fa0
Fa0/19 Desg FWD 19 128.19 P2p Fa0/20 Desg FWD 19 0.20 P2p Fa0/21 Desg FWD 19 128.21 P2p Fa0/22 Desg FWD 19 0.22 P2p
On SW1:
SW1# show spanning-tree vlan 600 | begin Interface
Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Desg FWD 19 128.21 P2p
Fa0/20 Desg FWD 19 128.22 P2p Fa0/21 Altn BLK 19 128.23 P2p Fa0/22 Root FWD 19 128.24 P2p Interface Role Sts Cost Prio.Nbr Type
--- ---- --- --- --- --- Fa0/19 Root FWD 19 128.19 P2p
Fa0/20 Altn BLK 19 128.20 P2p Fa0/21 Desg FWD 19 128.21 P2p Fa0/22 Desg FWD 19 128.22 P2p
ptg19878261
On SW4:
SW4# show spanning-tree vlan 600 | begin Interface
Interface Role Sts Cost Prio.Nbr Type
Erase the config.text and vlan.dat files and reload the switches before proceeding to the next lab.