1. Prepared by: PACE Academy (www.pace.net.pk) 1

2. TRADITIONAL SPANNING TREE SPANNING-TREE CONFIGURATION PROTECTING THE SPANNING TREE PROTOCOL TOPOLOGY ADVANCED SPANNING TREE PROTOCOL Spanning Tree Protocol 2

3. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Overview STP Summary and flavors STP FlavorsCisco ProprietaryIEEE Standard TraditionalPVST+CST 802.1Q old 802.1D One instance per VLANOne instance for all VLANs RapidRPVST+RST 802.1w, later 802.1D-2004 One instance for all VLANs One instance per VLAN Multiple MST 802.1s (Later 802.1Q 2005) Different VLANs can be mapped to different instances Required 802.1w for operation 3

4. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Bridge Protocol Data Units Configuration BPDUs -During the root bridge election send by all switches -After the root election sent only by the root -By default every 2 seconds -802.1D destination is 0180.C200.0000 -PVST sends to the above and to 100.0CCC.CCCD -Important Flags are: -Topology Change (TC) -Topology Change Acknowledgement(TCA) -Topology Change Notification (TCN) -Generated by the switch with a "direct change" 4

5. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Timers Hello Time Interval between BPDU transmissions By default 2 seconds Forward Delay The time interval ports spend in transient states By default 15 seconds Maximum Age (MaxAge) Maximum time switch will keep "the best" BPDU By default 20 seconds All timers can be modified Directly Indirectly using the "diameter" based calculation 5

6. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol STP Root Bridge 6

7. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol STP Configuration Commands Configuration CommandsTask Command Syntax  Enable STP.Switch(config)# spanning-tree vlan-id  Set bridge priority.Switch(config)# spanning-tree vlan vlan-id priority bridgepriority  Set root bridge (macro). Switch(config)# spanning-tree vlan vlan-id root { primary | secondary } [ diameter diameter ]  Set port cost.Switch(config-if)# spanning-tree [ vlan vlan-id ] cost cost Switch(config-if)# spanning-tree vlan 10 cost 2 or spanning-tree cost 8  Set port priority.Switch(config-if)# spanning-tree [ vlan vlan-id ] port-priority port-priority  Set STP timers.Switch(config)# spanning-tree [ vlan vlan-id ] hello-time seconds Switch(config)# spanning-tree hello-time 1 Switch(config)#spanning-tree [ vlan vlan-id ] forward-time seconds Switch(config)#spanning-tree [ vlan vlan-id ] max-age seconds  Set PortFast on an interface.Switch(config-if)# spanning-tree portfast  Set UplinkFast on a switch.Switch(config)# spanning-tree uplinkfast [ max-update-rate pkts-per-second ]  Set BackboneFast on a switch. Switch(config)# spanning-tree backbonefast 7

8. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Troubleshooting and Show Commands for STP and Task Command Syntax STP Monitoring Commands  show spanning-tree vlan 1  show spanning-tree vlan 1 bri  switch# show spanning tree  switch# show spanning-tree detail  switch# show spanning-tree vlan 1 summary  switch# show spanning-tree vlan 1 root  switch# show spanning-tree vlan 1 bridge  switch# show spanning-tree interface fa0/1  switch# show spanning-tree uplinkfast  switch# show spanning-tree backbonefast  show spanning-tree interface gigabitethernet 1/0/10 portfast 8

9. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol STP Port States 9

10. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Topology Change -Direct Topology Change Port moves into Forwarding, Blocking, or Disabled state -Indirect Topology Change Switch stops receiving Superior BPDUs After MaxAge* expires, topology change occurs -Signaling Topology Changes TCN BPDU is sent by the switch detecting a change Root port only Hello Time until Forwarded Delay expires or TCA is received on incoming BPDU -Root receives TCN and sets TC in BPDUs -Switches receiving BPDU with TC bit lower their MAC aging timers to Forward Delay Condition exists for the duration of MaxAge + Forwarded Delay 10

11. Prepared by: PACE Academy (www.pace.net.pk) Traditional Spanning Tree STP Hello Timer and Types of STP 11

12. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Features that decrease STP Convergence Time Uplink Fast 1.Typically configured on all Access layer switches 2.Globally enabled on a switch 3.Reacts to an direct link failure 4.Don’t apply on transit switches. 5.Don’t need to configure in configuring Rapid Spanning Tree for Network 6.In order to educate the other switches the infected switch sends dummy multicast frames containing the Source MAC address of access layers devices of infected switch to all other switches. 7.How we setup backboneFast a.Sw1(config)# Spanning-tree uplinkfast b.Sw1(config)# exit c.Sw1# show spanning-tree uplinkfast 12

13. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Features that decrease STP Convergence Time BackboneFast 1.Typically configured on all network switches 2.Globally enabled on a switch 3.Reacts to an indirect link failure 4.Don’t need to configure in configuring Rapid 5.Spanning Tree for Network 6.When indirect link failed the infected switch sends the inferior BPDUs to the non-root switches and by default without backboneFast the non-root switches ignores the inferior BPDUs and the link has to wait till 20-seconds for MAX-AGE time need to expire and the to process listening and learning stages 7.If backboneFast enabled then non-root switch sends the confirmation BPDU to root switch does it have a root to root bridge (send Root link Query RLQ – Root bridge reply called RLQ Reply). 8.How we setup backboneFast a. Sw1(config)# Spanning-tree backbonefast b.Sw1(config)# exit c. Sw1# show spanning-tree backbonefast 13

14. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Features that decrease STP Convergence Time PortFast 1.Typically configured on ports connecting to network endpoints 2.Globally enabled on a switch or on a port-by- port basis (for non-trunking ports) 3.Allows a switch port to go active almost immediately when an end station is attached to the port 4.How we setup backboneFast on per port basis a.Sw1(config)# interface fa 1/0/1 b.Sw1(config-if)# spanning-tree portfast c.Sw1(config-if)# exit 5.How we setup backboneFast globally a.Sw1(config)# Spanning-tree portfast default b.Sw1(config)# exit c.Sw1# show spanning-tree interface fa 1/0/1 portfast 14

15. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Features that increase STP stability BPDU Guard 1.Should be enabled on ports with Portfast enabled 2.Can be enabled globally or on a port-by-port basis (for ports with portfast enabled) 3.Causes a port to go into an error-diabled state if a BPDU is received 4.We need to physical shut and no shut to recover error disable state 5.How we setup backboneFast on per port basis a.Sw1(config)# interface fa 1/0/1 b.Sw1(config-if)# spanning-tree bpduguard enable c.Sw1(config-if)# exit d.Sw1(config-if)# no spanning-tree bpduguard enable 6.How we setup bpdu guard globally a.Sw1(config)# Spanning-tree portfast bpduguard default b.Sw1(config)# exit c.Sw1# show spanning-tree summary 15

16. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Features that increase STP stability BPDU Filter 1.Prevents a port from sending BPDUs 2.Can be enabled globally or on a port-by-port basis (for ports with portfast enabled) 3.Should only be used when necessary 4.Most dangerous when enabled at the port level 5.How we setup backboneFast on per port basis a.Sw1(config)# interface fa 1/0/1 b.Sw1(config-if)# spanning-tree bpdufulter enable c.Sw1(config-if)# exit d.Sw1# show spanning-tree int fa 1/0/1 detail This port will not send any bpdu and will ignore receiving or incoming bpdus therefor it could case loop 6.How we setup bpdu guard globally a.Sw1(config)# Spanning-tree portfast bpdufilter default b.Sw1(config)# exit c.Sw1# show spanning-tree summary In this case if port receives bpdus it will lose its portfast status. Switch becomes conscious. 16

17. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Features that increase STP stability Root Guard 1.Configured on ports off of which the root bridge is unexpected 2.By default it is disabled 3.Ports enabled for rootguard enter a root inconsistent state when receiving superior BPDUs 4.How we setup backboneFast on per polrt basis a.Sw1(config)# interface fa 1/0/1 b.Sw1(config-if)# spanning-tree guard root enable c.Sw1(config-if)# exit d.Sw1# show spanning-tree inconsistentports Root Guard can be configured at port level and it can not be configured Globally 17

18. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Features that increase STP stability Unidirectional Link Detectoion (UDLD) 1.Campus network Switches are connected by bidirectional link 2.Traffic can flow in two directions 3.What if TX of One GBIC circuit fails and links becomes Unidirectional 4.Cisco proprietary unidirectional link detection STP feature 5.Well known MAC = 01:00:0c:cc:cc:cc 6.UDLD uses Echo’s to verify the link is truly Bidirectional 7.UDLD timer is 15 seconds what should be UDLD MAX Timer?? 8.Normal Mode >> normal operation (just block that port having undetermined state and generate sys log message) 9.Aggressive Mode >> UDLD Message every second for 8 seconds and then put the port in error disable state (recommended mode) 10.UDLD ENABLE 11.Is it ok to enable UDLD on production Network? 12.UDLD Etherchannel 13.Switch(config-if)# udld { enable | aggressive | disable } 14.Once UDLD aggressive mode has put a switch port into the errdisable state, you must 15.use the following command to re-enable it: 16.Switch# udld reset 18

19. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Advanced Spanning Tree Protocol Rapid Spanning Tree Protocol (802.1w) and RPVST+ 19

20. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Advanced Spanning Tree Protocol (RSTP) 1.Synchronization: -Switch sends BPDU and proposes its port to be designated -Other switch sends superior BPDU (its own proposal Or -Other switch sends Agreement after to Synchronization 2.Works only on point to point ports -Full Duplex -Manually configured 3.Switch can detect a neighbor failure in three Hello intervals (default 6 seconds), versus the Max Age timer interval (default 20 seconds) for 802.1D. 4.How we setup RSTP globally a.Sw1(config)# Spanning-tree mode rapid-pvst b.Sw1(config)# exit c.Sw1# show spanning-tree summary 5.Creating vlan instances for rapid-pvst and giving ROLEs a.Sw1(config)# Spanning-tree vlan 100,300 root primary b.Sw1(config)# spanning-tree vlan 200 root secondary c.Sw1(config)# spanning tree link-type point-to-point or shared c.Sw1# show spanning-tree summary d.Sw1# show spanning-tree vlan 300 20

21. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Multiple Spanning Tree Protocol (MSTP) 802.1s 21

22. Prepared by: PACE Academy (www.pace.net.pk) 22 Spanning Tree Protocol Multiple Spanning Tree Protocol (MSTP) 802.1s 1.How we setup MSTP globally a.Sw1(config)# Spanning-tree instance configuration b.Sw1(config-mst)# instance 1 vlan 100,300 c. Sw1(config-mst)# instance 2 vlan 200 d. Sw1(config-mst)# spanning-tree mst 1 root primary e. Sw1(config-mst)# spanning-tree mst 2 root secondary f.Sw1 (config)# spanning tree mode mst Show spanning-tree mst configuration Show spanning-tree mst configuration digest Show spanning-tree summary

23. Prepared by: PACE Academy (www.pace.net.pk) Spanning Tree Protocol Multiple Spanning Tree Protocol (MSTP) 802.1s 23

24. Prepared by: PACE Academy (www.pace.net.pk) 'Allahumaf tah alaina hikmataka wanshur alaina rahmataka ya zul jalali wal ikram‘ Translation: Meaning 'O Allah, open the gates of knowledge and wisdom for us, and shower upon us your blessings. O Possessor of Majesty and Reverence' 'Allahumaf tah alaina hikmataka wanshur alaina rahmataka ya zul jalali wal ikram‘ Translation: Meaning 'O Allah, open the gates of knowledge and wisdom for us, and shower upon us your blessings. O Possessor of Majesty and Reverence' 24