05 Bcmsn Spanning Tree

149Boson NetSim for CCNP Lab Manual

Lab 5: Spanning Tree Protocol

ObjectiveObserve the default spanning tree, configure the Spanning Tree Protocol, and verify the spanning tree configura-tion.

Lab TopologyFor this lab, your network design will include two pods of devices. You will be responsible for configuring the devices in both pods. The devices on the left side of the topology are in Pod 1. The devices on the right side of the topology are in Pod 2. P1PC1 and P2PC2 are PC workstations. P1ASW1 and P2ASW2 are access-layer switches. P1DSW1 and P2DSW2 are distribution-layer switches. The access and distribution layers are two of the three lay-ers in the Cisco three-layer hierarchical network model, which also includes the core layer.

The Topology diagram below represents the NetMap in the Simulator. To access each of the devices from within the Simulator, select the device name from the appropriate menu in the Simulator. For example, to access P1ASW1, click the eSwitches button and select P1ASW1 from the drop-down menu.

BCMSN LAB 5Spanning Tree Protocol

150 Boson NetSim for CCNP Lab Manual

Command SummaryCommand Description

interface fastethernet slot/port configures an interface

interface range fastethernet slot/starting_port – ending_port

configures a range of interfaces

show interface stats displays statistics for packets and the switching method used

show spanning-tree vlan vlan displays spanning tree for a VLAN

show spanning-tree vlan vlan detail displays spanning tree detail

shutdown; no shutdown disables an interface; enables an interface

spanning-tree vlan vlan_id {root {primary | sec-ondary]

configures spanning tree root bridge

show spanning tree root displays root bridge per VLAN

spanning-tree vlan vlan_id priority priority sets spanning tree priority for use in the bridge ID

spanning-tree guard root sets root guard

spanning-tree uplinkfast sets uplinkfast

show spanning-tree uplinkfast verifies uplinkfast configuration

show interfaces interface_id switchport displays the switchport configuration

ping ip_address sends an ICMP echo request

Lab TasksTask 1: View Default Spanning Tree

Display the spanning tree for VLAN 1. Use the detail option. Use the output to answer questions about the spanning tree. a. Which spanning tree is VLAN 1 executing? ________________________________________________________________ b. What is the bridge ID? ________________________________________________________________ c. Why is there no root port? ________________________________________________________________ d. Why are there no blocked ports for VLAN 1? ________________________________________________________________ e. What is the timer value for sending bridge protocol data units (BPDUs)? ________________________________________________________________ f. What is the maximum age for a BPDU? ________________________________________________________________ g. What is the value of the forward delay timer? ________________________________________________________________

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BCMSN LAB 5Spanning Tree Protocol


Here is the output from a non-root switch. P2ASW2#show spanning-tree vlan 1 detail VLAN0001 is executing the ieee compatible Spanning Tree protocol Bridge Identifier has priority 32768, sysid 1, address 000a.f435.1200 Configured hello time 5, max age 40, forward delay 30 Current root has priority 32769, address 000a.41bf.0a40 Root port is 3 (FastEthernet0/3), cost of root path is 38 Topology change flag not set, detected flag not set Number of topology changes 49 last change occurred 08:43:53 ago Times: hold 1, topology change 35, notification 2 hello 2, max age 20, forward delay 15 Timers: hello 0, topology change 0, notification 0, aging 300 Port 1 (FastEthernet0/1) of VLAN0001 is blocking Port path cost 19, Port priority 128, Port Identifier 128.1. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000b.5f23.ed00 Designated port id is 128.15, designated path cost 19 Timers: message age 3, forward delay 0, hold 0 Number of transitions to forwarding state: 1 BPDU: sent 43, received 15759 Port 2 (FastEthernet0/2) of VLAN0001 is blocking Port path cost 19, Port priority 128, Port Identifier 128.2. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000b.5f23.ed00 Designated port id is 128.16, designated path cost 19 Timers: message age 3, forward delay 0, hold 0 Number of transitions to forwarding state: 1 BPDU: sent 46, received 15743 Port 3 (FastEthernet0/3) of VLAN0001 is forwarding Port path cost 19, Port priority 128, Port Identifier 128.3. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000b.5f23.eb00 Designated port id is 128.15, designated path cost 19 Timers: message age 2, forward delay 0, hold 0 Number of transitions to forwarding state: 1 BPDU: sent 161, received 15706

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Spanning Tree ProtocolBCMSN LAB 5


Port 4 (FastEthernet0/4) of VLAN0001 is blocking Port path cost 19, Port priority 128, Port Identifier 128.4. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000b.5f23.eb00 Designated port id is 128.16, designated path cost 19 Timers: message age 2, forward delay 0, hold 0 Number of transitions to forwarding state: 1 BPDU: sent 144, received 15692 Port 5 (FastEthernet0/5) of VLAN0001 is forwarding Port path cost 100, Port priority 128, Port Identifier 128.5. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000a.f435.1200 Designated port id is 128.5, designated path cost 38 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1 BPDU: sent 39928, received 0 Review the output above, and answer the following questions. a. What is the bridge ID? ________________________________________________________________ b. What is the root bridge ID? ________________________________________________________________ c. What is the root port? ________________________________________________________________ d. What is the cost for using the root port? ________________________________________________________________ e. What is the cost of the root path? Why is this cost different? _________________________________________________________________ f. What is the configured value for hello time, max age, and forward delay? ________________________________________________________________ g. Are these the timers that are in effect? Why or why not? _________________________________________________________________

Task 2: Configure the Root Bridge VLAN Root Bridge Secondary Root Bridge 11 P1DSW1 P2DSW2 12 P2DSW2 P1DSW1

Using the table above, assign the proper DSW as the root bridge for your VLAN.Display the Spanning Tree for your VLAN to verify that it is the root. Assign the proper DSW as the secondary root bridge for your VLAN. Display the spanning tree for your VLAN to verify that it is the secondary root.

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Lab SolutionsTask 1: View Default Spanning Tree

P1ASW1#show spanning-tree vlan 1 detail VLAN0001 is executing the ieee compatible Spanning Tree protocol Bridge Identifier has priority 32768, sysid 1, address 000a.41bf.0a40 Configured hello time 2, max age 20, forward delay 15 We are the root of the spanning tree Topology change flag not set, detected flag not set Number of topology changes 43 last change occurred 01:55:00 ago Times: hold 1, topology change 35, notification 2 hello 2, max age 20, forward delay 15 Timers: hello 1, topology change 0, notification 0, aging 300 Port 1 (FastEthernet0/1) of VLAN0001 is forwarding Port path cost 19, Port priority 128, Port Identifier 128.1. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000a.41bf.0a40 Designated port id is 128.1, designated path cost 0 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 2 Link type is point-to-point by default : sent 42807, received 20345 Port 2 (FastEthernet0/2) of VLAN0001 is forwarding Port path cost 19, Port priority 128, Port Identifier 128.2. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000a.41bf.0a40 Designated port id is 128.2, designated path cost 0 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 2 Link type is point-to-point by default BPDU: sent 42454, received 20247 Port 3 (FastEthernet0/3) of VLAN0001 is forwarding Port path cost 19, Port priority 128, Port Identifier 128.3. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000a.41bf.0a40 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 Link type is point-to-point by default BPDU: sent 3651, received 29

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Port 4 (FastEthernet0/4) of VLAN0001 is forwarding Port path cost 19, Port priority 128, Port Identifier 128.4. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000a.41bf.0a40 Designated port id is 128.4, 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 BPDU: sent 3641, received 6 Port 5 (FastEthernet0/5) of VLAN0001 is forwarding Port path cost 100, Port priority 128, Port Identifier 128.5. Designated root has priority 32769, address 000a.41bf.0a40 Designated bridge has priority 32769, address 000a.41bf.0a40 Designated port id is 128.5, designated path cost 0 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1 Link type is shared by default BPDU: sent 3768, received 0 a. VLAN 1 is executing IEEE. b. The bridge ID has priority 32768, sysid 1, and address 000a.41bf.0a40. c. There is no root port because this is the root bridge. d. There are no blocked ports for VLAN 1 because all ports on the root bridge are designated ports. e. The timer value for sending BPDUs is 2 seconds. f. The maximum age for a BPDU is 20 seconds. g. The value of the forward delay timer is 15 seconds.

a. The bridge ID has priority 32768, sysid 1, and address 000a.f435.1200. b. The current root has priority 32769 and address 000a.41bf.0a40. c. The root port is 3 (FastEthernet0/3). d. The cost for using the root port is 19. e. The cost of the root path is 38. This device is not directly connected to the root. Path cost is additive. f. The configured hello time is 5, the max age is 40, and the forward delay is 30. g. These timers are not in effect. The timers that are in effect are the timers advertised by the root bridge.

Task 2: Configure the Root Bridgespanning-tree vlan 11 root primaryP1DSW1#show spanning-tree vlan 11 VLAN0011 Spanning tree enabled protocol ieee

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Root ID Priority 24587 Address 000b.5f23.ed00 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 24587 (priority 24576 sys-id-ext 11) Address 000b.5f23.ed00 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ---------------- -------- --------- --- --------- -------------------- -------- Fa0/1 128.11 19 FWD 0 24587 000b.5f23.ed00 128.11 Fa0/2 128.12 19 FWD 0 24587 000b.5f23.ed00 128.12 Fa0/3 128.15 19 FWD 0 24587 000b.5f23.ed00 128.15 Fa0/4 128.16 19 FWD 0 24587 000b.5f23.ed00 128.16spanning-tree vlan 11 root secondary P2DSW2#show spanning-tree vlan 11 VLAN0011 Spanning tree enabled protocol ieee Root ID Priority 24587 Address 000b.5f23.ed00 Cost 38 Port 15 (FastEthernet0/15) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 28683 (priority 28672 sys-id-ext 11) Address 000b.5f23.eb00 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ---------------- -------- --------- --- --------- -------------------- -------- Fa0/1 128.11 19 FWD 38 28683 000b.5f23.eb00 128.11 Fa0/2 128.12 19 FWD 38 28683 000b.5f23.eb00 128.12 Fa0/3 128.15 19 FWD 19 32779 000a.f435.1200 128.3 Fa0/4 128.16 19 BLK 19 32779 000a.f435.1200 128.4

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Sample Configuration ScriptsP1DSW1 P1DSW1 (Continued)

version 12.1!hostname P1DSW1!ip subnet-zerono ip domain-lookup!!interface FastEthernet0/1 description P1DSW1 to P1ASW1 switchport trunk encapsulation dot1q no ip address duplex full speed 100!interface FastEthernet0/2 description P1DSW1 to P1ASW1 switchport trunk encapsulation dot1q no ip address duplex full speed 100!interface FastEthernet0/3 description P1DSW1 to P2ASW2 switchport trunk encapsulation dot1q no ip address duplex full speed 100!interface FastEthernet0/4 description P1DSW1 to P2ASW2 switchport trunk encapsulation dot1q no ip address duplex full speed 100!!interface FastEthernet0/5 no ip address!interface FastEthernet0/6 no ip address!interface FastEthernet0/7 no ip address!interface FastEthernet0/8 no ip address!

interface FastEthernet0/9 no ip address!interface FastEthernet0/10 no ip address!interface FastEthernet0/23 switchport trunk encapsulation dot1q switchport mode trunk no ip address!interface FastEthernet0/24 switchport trunk encapsulation dot1q switchport mode trunk no ip address!interface GigabitEthernet0/1 no ip address!interface GigabitEthernet0/2 no ip address!interface Vlan1 ip address 172.16.1.100 255.255.0.0 shutdown!interface Vlan99 ip address 172.16.99.100 255.255.0.0!ip classlessip http server!line con 0 password cisco loginline vty 0 4 password cisco loginline vty 5 15 login!end


05 Bcmsn Spanning Tree

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