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Four switches have just been installed. The distribution layer switches are Catalyst 3560s, and the access layer switches are Catalyst 2960s. There are redundant uplinks between the access layer and distribution layer. Because of the possibility of bridging loops, spanning tree logically removes any redundant links. In this lab, you will see what happens when spanning tree is configured differently for different VLANs.
All Switches: interface range f0/7-12 switchport trunk encapsulation dot1q switchport mode trunk
a. Configure all switches with VTP mode transparent and VTP domain CISCO. Add VLAN 10 and 20 to all of them. Use the show vlan brief command to view the VLAN configurations.
All Switch: vtp mode transparent vtp domain CISCO vlan 10,20
IOU1#show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Et1/2, Et1/3, Et2/0, Et2/1
Et2/2, Et2/3, Et3/0, Et3/1
Et3/2, Et3/3
10 VLAN0010 active
20 VLAN0020 active
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
b. Issue the show spanning-tree command on any of the four switches. Notice that instead of just one VLAN there are non-reserved VLAN. VLAN 1002-1005 are reserved for internal switch usage. All other VLAN shown are non-reserved.
Note: By default Cisco switches use PVST+, a Cisco-proprietary IEEE 802.1Q-compatible per-VLAN spanning tree protocol.
IOU1#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address aabb.cc00.0100 Cost 100 Port 1 (Ethernet0/0) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address aabb.cc00.0500 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Root FWD 100 128.1 Shr Et0/1 Altn BLK 100 128.2 Shr Et0/2 Altn BLK 100 128.3 Shr Et0/3 Altn BLK 100 128.4 Shr Et1/0 Altn BLK 100 128.5 Shr Et1/1 Altn BLK 100 128.6 Shr Et1/2 Desg FWD 100 128.7 Shr Et1/3 Desg FWD 100 128.8 Shr Et2/0 Desg FWD 100 128.9 Shr Et2/1 Desg FWD 100 128.10 Shr Et2/2 Desg FWD 100 128.11 Shr Et2/3 Desg FWD 100 128.12 Shr Et3/0 Desg FWD 100 128.13 Shr Et3/1 Desg FWD 100 128.14 Shr Et3/2 Desg FWD 100 128.15 Shr Et3/3 Desg FWD 100 128.16 Shr VLAN0010 Spanning tree enabled protocol ieee Root ID Priority 32778 Address aabb.cc00.0100 Cost 100 Port 1 (Ethernet0/0) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32778 (priority 32768 sys-id-ext 10) Address aabb.cc00.0500 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Root FWD 100 128.1 Shr Et0/1 Altn BLK 100 128.2 Shr Et0/2 Altn BLK 100 128.3 Shr Et0/3 Altn BLK 100 128.4 Shr Et1/0 Altn BLK 100 128.5 Shr Et1/1 Altn BLK 100 128.6 Shr VLAN0020 Spanning tree enabled protocol ieee Root ID Priority 32788 Address aabb.cc00.0100 Cost 100 Port 1 (Ethernet0/0) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32788 (priority 32768 sys-id-ext 20) Address aabb.cc00.0500 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Root FWD 100 128.1 Shr Et0/1 Altn BLK 100 128.2 Shr Et0/2 Altn BLK 100 128.3 Shr Et0/3 Altn BLK 100 128.4 Shr Et1/0 Altn BLK 100 128.5 Shr Et1/1 Altn BLK 100 128.6 Shr
Notice that all the ports have identical spanning tree behavior for each VLAN. This is because all VLANs are running spanning tree with the default behavior. However, you can modify the default spanning tree behavior on a per-VLAN basis. The default priority is 32768. Configuring a switch with a lower priority value for a given VLAN makes it the root bridge for that VLAN. For this lab, we assign DLS1 as the root bridge for VLAN 10, and DLS2 for VLAN 20.
DLS1(config)#spanning-tree vlan 10 priority 4096 DLS2(config)#spanning-tree vlan 20 priority 4096
IOU1#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address aabb.cc00.0100 Cost 100 Port 1 (Ethernet0/0) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address aabb.cc00.0500 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Root FWD 100 128.1 Shr Et0/1 Altn BLK 100 128.2 Shr Et0/2 Altn BLK 100 128.3 Shr Et0/3 Altn BLK 100 128.4 Shr Et1/0 Altn BLK 100 128.5 Shr Et1/1 Altn BLK 100 128.6 Shr Et1/2 Desg FWD 100 128.7 Shr Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et1/3 Desg FWD 100 128.8 Shr Et2/0 Desg FWD 100 128.9 Shr Et2/1 Desg FWD 100 128.10 Shr Et2/2 Desg FWD 100 128.11 Shr Et2/3 Desg FWD 100 128.12 Shr Et3/0 Desg FWD 100 128.13 Shr Et3/1 Desg FWD 100 128.14 Shr Et3/2 Desg FWD 100 128.15 Shr Et3/3 Desg FWD 100 128.16 Shr VLAN0010 Spanning tree enabled protocol ieee Root ID Priority 4106 Address aabb.cc00.0500 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 4106 (priority 4096 sys-id-ext 10) Address aabb.cc00.0500 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 15 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Desg FWD 100 128.1 Shr Et0/1 Desg FWD 100 128.2 Shr Et0/2 Desg FWD 100 128.3 Shr Et0/3 Desg FWD 100 128.4 Shr Et1/0 Desg FWD 100 128.5 Shr Et1/1 Desg FWD 100 128.6 Shr VLAN0020 Spanning tree enabled protocol ieee Root ID Priority 4116 Address aabb.cc00.0100 Cost 100 Port 1 (Ethernet0/0) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32788 (priority 32768 sys-id-ext 20) Address aabb.cc00.0500 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Root FWD 100 128.1 Shr Et0/1 Altn BLK 100 128.2 Shr Et0/2 Altn BLK 100 128.3 Shr Et0/3 Altn BLK 100 128.4 Shr Et1/0 Altn BLK 100 128.5 Shr Et1/1 Altn BLK 100 128.6 Shr
IOU2#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address aabb.cc00.0100 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address aabb.cc00.0100 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Desg FWD 100 128.1 Shr Et0/1 Desg FWD 100 128.2 Shr Et0/2 Desg FWD 100 128.3 Shr Et0/3 Desg FWD 100 128.4 Shr Et1/0 Desg FWD 100 128.5 Shr Et1/1 Desg FWD 100 128.6 Shr Et1/2 Desg FWD 100 128.7 Shr Et1/3 Desg FWD 100 128.8 Shr Et2/0 Desg FWD 100 128.9 Shr Et2/1 Desg FWD 100 128.10 Shr Et2/2 Desg FWD 100 128.11 Shr Et2/3 Desg FWD 100 128.12 Shr Et3/0 Desg FWD 100 128.13 Shr Et3/1 Desg FWD 100 128.14 Shr Et3/2 Desg FWD 100 128.15 Shr Et3/3 Desg FWD 100 128.16 Shr VLAN0010 Spanning tree enabled protocol ieee Root ID Priority 4106 Address aabb.cc00.0500 Cost 100 Port 1 (Ethernet0/0) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32778 (priority 32768 sys-id-ext 10) Address aabb.cc00.0100 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Root FWD 100 128.1 Shr Et0/1 Altn BLK 100 128.2 Shr Et2/0 Desg FWD 100 128.9 Shr Et2/1 Desg FWD 100 128.10 Shr Et2/2 Desg FWD 100 128.11 Shr Et2/3 Desg FWD 100 128.12 Shr VLAN0020 Spanning tree enabled protocol ieee Root ID Priority 4116 Address aabb.cc00.0100 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 4116 (priority 4096 sys-id-ext 20) Address aabb.cc00.0100 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Et0/0 Desg FWD 100 128.1 Shr Et0/1 Desg FWD 100 128.2 Shr Et2/0 Desg FWD 100 128.9 Shr Et2/1 Desg FWD 100 128.10 Shr Et2/2 Desg FWD 100 128.11 Shr Et2/3 Desg FWD 100 128.12 Shr
Other spanning tree modes besides PVST+ are available. One of these is RSTP (rapid spanning tree protocol), which greatly reduces the time for a port to transition to forwarding state while still preventing bridging loops. Cisco-proprietary per-VLAN rapid spanning tree (PVRST+) combines the functionality of RSTP and PVST.
Note: You can use the clear spanning-tree detected-protocols command after configuring different spanning tree modes. This can avoid a mutual deadlock between two switches when they consider themselves as 802.1D legacy bridges when in fact they were configured for RSTP.
a. To change the spanning tree mode to PVST+, use the global configuration command spanning-tree mode rapid-pvst. Configure this on all four switches. During the transition period, rapid spanning tree falls back to 802.1D spanning tree on the links that have 802.1D spanning tree configured on one side.
All switches:
spanning-tree mode rapid-pvst
a. On each switch, add VLAN 50,60,70,80.90,100. Configure ALS1 to be the root bridge for VLAN 50,60,70. and ALS2 to be the root bridge for VLAN 80,90 and 100. Configure the root bridges with a single line on each switch.
HINT: Use the question mark when you type the global configuration command spanning-tree vlan?. Notice that you can modify spanning tree attributes in ranges.
b. Change the spanning tree cost of VLAN20 on f0/11 and f0/12 between DLS1 AND DLS2 TO 15.
Lab - Per-VLAN Spanning Tree Behavior
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原文地址：http://www.cnblogs.com/elewei/p/4780369.html
