Topologi
Objectives
• Observe the behavior of a separate spanning tree instance per VLAN.
• Change spanning tree mode to rapid spanning tree.
Background
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.
Genomförande
Vi börjar med lite grundkonfig för respektive switch.
S1
Switch(config)#hostname S1 S1(config)#line con 0 S1(config-line)#logging synchronous S1(config-line)#exit S1(config)#int range fa0/1 - 2 S1(config-if-range)#switchport trunk encapsulation dot1q S1(config-if-range)#switchport mode dynamic desirable S1(config-if-range)#description to S2 S1(config-if-range)#int range fa0/3 - 4 S1(config-if-range)#switchport trunk encapsulation isl S1(config-if-range)#switchport mode dynamic desirable S1(config-if-range)#description to S3 S1(config-if-range)#exit S1(config)#vtp mode server Device mode already VTP SERVER. S1(config)#vtp domain Cisco Changing VTP domain name from NULL to Cisco S1(config)#vtp password cisco Setting device VLAN database password to cisco S1(config)#vtp version 2 S1(config)#vlan 10,20,50,60,70,80,90,100 S1(config-vlan)#exit S1#sh interface trunk Port Mode Encapsulation Status Native vlan Fa0/1 desirable 802.1q trunking 1 Fa0/2 desirable 802.1q trunking 1 Fa0/3 desirable isl trunking 1 Fa0/4 desirable isl trunking 1 Port Vlans allowed and active in management domain Fa0/1 1,10,20,50,60,70,80,90,100 Fa0/2 1,10,20,50,60,70,80,90,100 Fa0/3 1,10,20,50,60,70,80,90,100 Fa0/4 1,10,20,50,60,70,80,90,100
S3
Switch(config)#hostname S3 S3(config)#line con 0 S3(config-line)#logging synchro S3(config-line)#int range fa0/1 - 2 S3(config-if-range)#switchport trunk encapsulation dot1q S3(config-if-range)#switchport mode dynamic desirable S3(config-if-range)#description to S2 S3(config-if-range)#int range fa0/3 - 4 S3(config-if-range)#switchport trunk encapsulation isl S3(config-if-range)#switchport mode dynamic auto S3(config-if-range)#description to S1 S3(config-if-range)#exit S3(config)#vtp mode client Setting device to VTP CLIENT mode. S3(config)#vtp domain Cisco Changing VTP domain name from NULL to Cisco S3(config)#vtp password cisco Setting device VLAN database password to cisco 3#sh interface trunk Port Mode Encapsulation Status Native vlan Fa0/1 desirable 802.1q trunking 1 Fa0/2 desirable 802.1q trunking 1 Fa0/3 auto isl trunking 1 Fa0/4 auto isl trunking 1 Port Vlans allowed and active in management domain Fa0/1 1,10,20,50,60,70,80,90,100 Fa0/2 1,10,20,50,60,70,80,90,100 Fa0/3 1,10,20,50,60,70,80,90,100 Fa0/4 1,10,20,50,60,70,80,90,100
S2
Switch(config)#hostname S2 S2(config)#line con 0 S2(config-line)#logging sync S2(config-line)#int range fa0/1 - 2 S2(config-if-range)#switchport trunk encaps S2(config-if-range)#switchport mode dynamic auto S2(config-if-range)#description to S1 S2(config-if-range)#int range fa0/3 - 4 S2(config-if-range)#switchport mode dynamic auto S2(config-if-range)#description to S3 S2(config-if-range)#exit S2(config)#vtp mode client Setting device to VTP CLIENT mode. S2(config)#vtp domain Cisco Changing VTP domain name from NULL to Cisco S2(config)#vtp *Mar 1 00:27:37.639: %SW_VLAN-6-VTP_DOMAIN_NAME_CHG: VTP domain name changed to Cisco. S2(config)#vtp password cisco Setting device VLAN database password to cisco S2#sh interface trunk Port Mode Encapsulation Status Native vlan Fa0/1 auto 802.1q trunking 1 Fa0/2 auto 802.1q trunking 1 Fa0/3 auto 802.1q trunking 1 Fa0/4 auto 802.1q trunking 1 Port Vlans allowed and active in management domain Fa0/1 1,10,20,50,60,70,80,90,100 Fa0/2 1,10,20,50,60,70,80,90,100 Fa0/3 1,10,20,50,60,70,80,90,100 Fa0/4 1,10,20,50,60,70,80,90,100
Enligt uppgiften ska S1 vara:
- Primary root-bridge för Vlan 10, 50, 60, 70
- Secondary root-bridge för Vlan 20, 80, 90, 100
Det fixar vi enkelt med följande kommando:
S1(config)#spanning-tree vlan 10,50,60,70 root primary S1(config)#spanning-tree vlan 20,80,90,100 root secondary
Och vice versa på S3:
S3(config)#spanning-tree vlan 10,50,60,70 root secondary S3(config)#spanning-tree vlan 20,80,90,100 root primary
Verifiera med:
S3#sh spanning-tree vlan 10 VLAN0010 Spanning tree enabled protocol ieee Root ID Priority 24586 Address 0024.c33f.9e80 Cost 19 Port 5 (FastEthernet0/3) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec S3#sh spanning-tree vlan 20 VLAN0020 Spanning tree enabled protocol ieee Root ID Priority 24596 Address 0014.a889.9c80 This bridge is the root
Vi skulle sedan ändra cost för Vlan20 till 15 mellan S1-S2’s Fa0/4 interface. Observera att fa0/3 just nu används som root-port på S1 till S3 (root-bridge) innan vi ändrar något, detta pga equal cost 19 – fa0/3 vinner med lägre port-id. Behöver endast ändra på S1 då S3 har alla portar som designated (root-bridge).
S1(config)#int fa0/4 S1(config-if)#spanning-tree vlan 20 cost 15 S1(config-if)#do sh spanning-tree vlan 20 VLAN0020 Spanning tree enabled protocol ieee Root ID Priority 24596 Address 0014.a889.9c80 Cost 15 Port 6 (FastEthernet0/4) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 28692 (priority 28672 sys-id-ext 20) Address 0024.c33f.9e80 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Fa0/1 Desg FWD 19 128.3 P2p Fa0/2 Desg FWD 19 128.4 P2p Fa0/3 Altn BLK 19 128.5 P2p Fa0/4 Root FWD 15 128.6 P2p
Vackert!
Vi skulle även byta till rapid-pvst:
S1(config)#spanning-tree mode rapid-pvst S2(config)#spanning-tree mode rapid-pvst S3(config)#spanning-tree mode rapid-pvst S3#sh spanning-tree vlan 20 VLAN0020 Spanning tree enabled protocol rstp Root ID Priority 24596 Address 0014.a889.9c80 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Klart!
