Cisco IOS Layer2 – MST (Multiple Spanning Tree) の設定

スポンサーリンク

MST(Multiple Spanning Tree Protocol : 802.1s)は、複数のVLANをひとつのインスタンスにまとめる機能です。複数VLANを1つにまとめる事によって、STP計算による負荷を軽減する事ができます。

概要

MST(Multiple Spanning Tree Protocol : 802.1s)は、複数のVLANをひとつのインスタンスにまとめる機能です。raipd-PVST+ (802.1w)の後続規格で、RSTP, backbone fastなどの機能はデフォルトで有効になっています。

複数のVLANをひとつにまとめる事によって、STP計算の負荷を抑える事ができます。raipd-PVST+による負荷に耐えられない場合はraipd-PVST+からMSTへの移行を図る事もあります。

コマンド一覧

このシナリオで重要なコマンド一覧は以下の通りです。

Switch(config)# spanning-tree mode mst
Switch(config)# spanning-tree mst hello-time <sec>
Switch(config)# spanning-tree mst forward-time <sec>
Switch(config)# spanning-tree mst max-age <sec>
Switch(config)# spanning-tree mst instance-id priority <priority>

Switch(config)# spanning-tree mst configuration
Switch(config-mst)# instance <instance-id> vlan <vlan-range>
Switch(config-mst)# name <name>
Switch(config-mst)# revision <number>

Switch(config)# interface <interface>
Switch(config-if)# spanning-tree mst instance-id cost <cost>
Switch(config-if)# spanning-tree mst instance-id port-priority <priority>

構成図

以下の物理構成で動作確認を行います。

[物理構成]
                 f0/13-15+------------+f0/16-18
         ┌--------------+            +--------------┐
         │┌------------+    SW 2    +------------┐│
         ││┌----------+            +----------┐││
         │││          +---+-+-+----+          │││
 f0/13-15│││              │││f0/19-21      │││f0/16-18
     +---+-+-+----+f0/16-18  │││          +---+-+-+----+
     |            +--------------------------+            |
     |    SW 1    +--------------------------+    SW 3    |
     |            +--------------------------+            |
     +---+-+-+----+          │││  f0/13-15+---+-+-+----+
 f0/19-21│││      f0/16-18│││              │││f0/19-21
         │││          +---+-+-+----+          │││
         ││└----------+            +----------┘││
         │└------------+    SW 4    +------------┘│
         └--------------+            +--------------┘
                 f0/13-15+------------+f0/19-21

shutdownコマンドコマンドを用いて、以下のような論理構成を再現します。

 [論理構成]
                 f0/13-15+------------+f0/16-18
         ┌--------------+            +--------------┐
         │┌------------+    SW 2    +------------┐│
         ││┌----------+            +----------┐││
         │││          +------------+          │││
 f0/13-15│││                                  │││f0/16-18
     +---+-+-+----+                          +---+-+-+----+
     |           |                           |           | 
     |    SW 1   |                           |    SW 3   | 
     |           |                           |           | 
     +---+-+-+----+                          +---+-+-+----+
 f0/19-21│││                                  │││f0/19-21
         │││          +------------+          │││
         ││└----------+            +----------┘││
         │└------------+    SW 4    +------------┘│
         └--------------+            +--------------┘
                 f0/13-15+------------+f0/19-21
[/code]
 [SW1]
interface range FastEthernet 0/16-18
 shutdown

 [SW2]
interface range FastEthernet 0/19-21
 shutdown

 [SW3]
interface range FastEthernet 0/13-15
 shutdown

 [SW4]
interface range FastEthernet 0/16-18
 shutdown

設定全文は下記ファイルです。詳細設定は下記を参照ください。

SW1
!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Rack15SW1
!
boot-start-marker
boot-end-marker
!
enable password cisco
!
no aaa new-model
system mtu routing 1500
vtp mode transparent
ip subnet-zero
ip routing
no ip domain-lookup
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
vlan 5,7-10,22,43,58,67,79,146
!
!
!
!
interface Loopback0
 ip address 150.15.7.7 255.255.255.0
 ip rip advertise 10
!
interface FastEthernet0/1
 switchport access vlan 146
!
interface FastEthernet0/2
!
interface FastEthernet0/3
 no switchport
 ip address 155.15.37.7 255.255.255.0
 ip rip advertise 10
!
interface FastEthernet0/4
!
interface FastEthernet0/5
 switchport access vlan 58
 switchport mode access
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
 switchport mode dynamic desirable
!
interface FastEthernet0/14
 switchport mode dynamic desirable
!
interface FastEthernet0/15
 switchport mode dynamic desirable
!
interface FastEthernet0/16
 switchport mode dynamic desirable
 shutdown
!
interface FastEthernet0/17
 switchport mode dynamic desirable
 shutdown
!
interface FastEthernet0/18
 switchport mode dynamic desirable
 shutdown
!
interface FastEthernet0/19
 switchport mode dynamic desirable
!
interface FastEthernet0/20
 switchport mode dynamic desirable
!
interface FastEthernet0/21
 switchport mode dynamic desirable
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
interface Vlan7
 ip address 155.15.7.7 255.255.255.0
 ip rip advertise 10
!
interface Vlan67
 ip address 155.15.67.7 255.255.255.0
 ip rip advertise 10
!
interface Vlan79
 ip address 155.15.79.7 255.255.255.0
 ip rip advertise 10
!
router rip
 version 2
 timers basic 10 40 30 60
 network 150.15.0.0
 network 155.15.0.0
 no auto-summary
!
ip classless
ip http server
ip http secure-server
!
!
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous level 0 limit 20
line vty 0 4
 password cisco
 login
line vty 5 15
 password cisco
 login
!
end
SW2
!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Rack15SW2
!
boot-start-marker
boot-end-marker
!
enable password cisco
!
no aaa new-model
system mtu routing 1500
vtp mode transparent
ip subnet-zero
ip routing
no ip domain-lookup
!
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
vlan 5,7-10,22,43,58,67,79,146
!
!
!
!
interface Loopback0
 ip address 150.15.8.8 255.255.255.0
 ip rip advertise 10
!
interface Port-channel1
 no switchport
 ip address 155.15.108.8 255.255.255.0
 ip rip advertise 10
!
interface FastEthernet0/1
!
interface FastEthernet0/2
 switchport access vlan 22
 switchport mode access
 spanning-tree portfast
!
interface FastEthernet0/3
!
interface FastEthernet0/4
 switchport access vlan 43
 switchport mode access
 spanning-tree portfast
!
interface FastEthernet0/5
!
interface FastEthernet0/6
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 67,146
 switchport mode trunk
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
 switchport mode dynamic desirable
!
interface FastEthernet0/14
 switchport mode dynamic desirable
!
interface FastEthernet0/15
 switchport mode dynamic desirable
!
interface FastEthernet0/16
 switchport mode dynamic desirable
!
interface FastEthernet0/17
 switchport mode dynamic desirable
!
interface FastEthernet0/18
 switchport mode dynamic desirable
!
interface FastEthernet0/19
 no switchport
 no ip address
 shutdown
 channel-group 1 mode on
!
interface FastEthernet0/20
 no switchport
 no ip address
 shutdown
 channel-group 1 mode on
!
interface FastEthernet0/21
 switchport mode dynamic desirable
 shutdown
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
 switchport access vlan 22
 switchport mode access
 spanning-tree portfast
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
interface Vlan8
 ip address 155.15.8.8 255.255.255.0
 ip rip advertise 10
!
interface Vlan58
 ip address 155.15.58.8 255.255.255.0
 ip rip advertise 10
!
router rip
 version 2
 timers basic 10 40 30 60
 network 150.15.0.0
 network 155.15.0.0
 no auto-summary
!
ip classless
ip http server
ip http secure-server
!
!
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous level 0 limit 20
line vty 0 4
 password cisco
 login
line vty 5 15
 password cisco
 login
!
end
SW3
!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Rack15SW3
!
enable password cisco
!
no aaa new-model
ip subnet-zero
ip routing
no ip domain-lookup
!
vtp file vlan.dat
vtp mode transparent
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
vlan 5,7-10,22,43,58,67,79,146
!
!
!
!
!
!
interface Loopback0
 ip address 150.15.9.9 255.255.255.0
 ip rip advertise 10
!
interface FastEthernet0/1
 switchport mode dynamic desirable
!
interface FastEthernet0/2
 switchport mode dynamic desirable
!
interface FastEthernet0/3
 switchport mode dynamic desirable
!
interface FastEthernet0/4
 switchport mode dynamic desirable
!
interface FastEthernet0/5
 switchport access vlan 5
 switchport mode access
 spanning-tree portfast
!
interface FastEthernet0/6
 switchport mode dynamic desirable
!
interface FastEthernet0/7
 switchport mode dynamic desirable
!
interface FastEthernet0/8
 switchport mode dynamic desirable
!
interface FastEthernet0/9
 switchport mode dynamic desirable
!
interface FastEthernet0/10
 switchport mode dynamic desirable
!
interface FastEthernet0/11
 switchport mode dynamic desirable
!
interface FastEthernet0/12
 switchport mode dynamic desirable
!
interface FastEthernet0/13
 switchport mode dynamic desirable
 shutdown
!
interface FastEthernet0/14
 switchport mode dynamic desirable
 shutdown
!
interface FastEthernet0/15
 switchport mode dynamic desirable
 shutdown
!
interface FastEthernet0/16
 switchport mode dynamic desirable
!
interface FastEthernet0/17
 switchport mode dynamic desirable
!
interface FastEthernet0/18
 switchport mode dynamic desirable
!
interface FastEthernet0/19
 switchport mode dynamic desirable
!
interface FastEthernet0/20
 switchport mode dynamic desirable
!
interface FastEthernet0/21
 switchport mode dynamic desirable
!
interface FastEthernet0/22
 switchport mode dynamic desirable
!
interface FastEthernet0/23
 switchport mode dynamic desirable
!
interface FastEthernet0/24
 switchport access vlan 43
 switchport mode access
 spanning-tree portfast
!
interface GigabitEthernet0/1
 switchport mode dynamic desirable
!
interface GigabitEthernet0/2
 switchport mode dynamic desirable
!
interface Vlan1
 no ip address
 shutdown
!
interface Vlan9
 ip address 155.15.9.9 255.255.255.0
 ip rip advertise 10
!
interface Vlan79
 ip address 155.15.79.9 255.255.255.0
 ip rip advertise 10
!
router rip
 version 2
 timers basic 10 40 30 60
 network 150.15.0.0
 network 155.15.0.0
 no auto-summary
!
ip classless
ip http server
ip http secure-server
!
!
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous level 0 limit 20
line vty 0 4
 password cisco
 login
line vty 5 15
 password cisco
 login
!
end
SW4
!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Rack15SW4
!
enable password cisco
!
no aaa new-model
ip subnet-zero
ip routing
no ip domain-lookup
!
vtp file vlan.dat
vtp mode transparent
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
vlan 5,7-10,22,43,58,67,79,146
!
!
!
!
!
!
interface Loopback0
 ip address 150.15.10.10 255.255.255.0
 ip rip advertise 10
!
interface Port-channel1
 no switchport
 ip address 155.15.108.10 255.255.255.0
 ip rip advertise 10
!
interface FastEthernet0/1
 switchport mode dynamic desirable
!
interface FastEthernet0/2
 switchport mode dynamic desirable
!
interface FastEthernet0/3
 switchport mode dynamic desirable
!
interface FastEthernet0/4
 switchport access vlan 146
 switchport mode access
!
interface FastEthernet0/5
 switchport mode dynamic desirable
!
interface FastEthernet0/6
 switchport mode dynamic desirable
!
interface FastEthernet0/7
 switchport mode dynamic desirable
!
interface FastEthernet0/8
 switchport mode dynamic desirable
!
interface FastEthernet0/9
 switchport mode dynamic desirable
!
interface FastEthernet0/10
 switchport mode dynamic desirable
!
interface FastEthernet0/11
 switchport mode dynamic desirable
!
interface FastEthernet0/12
 switchport mode dynamic desirable
!
interface FastEthernet0/13
 switchport mode dynamic desirable
!
interface FastEthernet0/14
 switchport mode dynamic desirable
!
interface FastEthernet0/15
 switchport mode dynamic desirable
!
interface FastEthernet0/16
 no switchport
 no ip address
 shutdown
 channel-group 1 mode on
!
interface FastEthernet0/17
 no switchport
 no ip address
 shutdown
 channel-group 1 mode on
!
interface FastEthernet0/18
 switchport mode dynamic desirable
 shutdown
!
interface FastEthernet0/19
 switchport mode dynamic desirable
!
interface FastEthernet0/20
 switchport mode dynamic desirable
!
interface FastEthernet0/21
 switchport mode dynamic desirable
!
interface FastEthernet0/22
 switchport mode dynamic desirable
!
interface FastEthernet0/23
 switchport mode dynamic desirable
!
interface FastEthernet0/24
 switchport mode dynamic desirable
!
interface GigabitEthernet0/1
 switchport mode dynamic desirable
!
interface GigabitEthernet0/2
 switchport mode dynamic desirable
!
interface Vlan1
 no ip address
 shutdown
!
interface Vlan10
 ip address 155.15.10.10 255.255.255.0
 ip rip advertise 10
!
router rip
 version 2
 timers basic 10 40 30 60
 network 150.15.0.0
 network 155.15.0.0
 no auto-summary
!
ip classless
ip http server
ip http secure-server
!
!
!
control-plane
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous level 0 limit 20
line vty 0 4
 password cisco
 login
line vty 5 15
 password cisco
 login
!
end

仕様説明

基本設定

以下のコマンドで、spanning-treeのmodeをpvstからmstに変更します。

Switch(config)# spanning-tree mode mst

以下のコマンドで、MSTの設定を行う事ができます。なお、mstの設定はVTP等で伝播させる事ができません。mstは全台に同じ設定を反映される必要があります。configuratoin name, revision number, instance-idとVLNAのマッピングは全スイッチで一致させる必要があります

Switch(config)# spanning-tree mst configuration
Switch(config-mst)# instance <instance-id> vlan <vlan-range>
Switch(config-mst)# name <name>
Switch(config-mst)# revision <number>

root portの制御

以下のコマンドで、bridge priority, cost, port-priorityを設定する事ができます。

Switch(config)# spanning-tree mst instance-id priority <priority>
Switch(config-if)# spanning-tree mst instance-id cost <cost>
Switch(config-if)# spanning-tree mst instance-id port-priority <priority>

timerの制御

以下のコマンドで、hello-time, forward-time, max-ageを変更する事ができます。

Switch(config)# spanning-tree mst hello-time <sec>
Switch(config)# spanning-tree mst forward-time <sec>
Switch(config)# spanning-tree mst max-age <sec>

基本設定

設定投入

全スイッチに対してMSTを設定します。configuration nameは"CCIE"、revision numberは20とします。instanceとVLANのマッピングは以下の表の通りとします。

instance vlan
0 instance 0には未定義のVLANが格納されます
1 5,7,8,9,10
2 22,43,58,67,79
3 146
 [SW1, SW2, SW3, SW4]
spanning-tree mode mst
!
spanning-tree mst configuration
 name CCIE
 revision 20
 instance 1 vlan 5,7,8,9,10
 instance 2 vlan 22,43,58,67,79
 instance 3 vlan 146

動作確認

show spanning-tree mst configurationコマンドにより設定を確認します。

 [SW1]
Rack15SW1#show spanning-tree mst configuration
Name      [CCIE]
Revision  20    Instances configured 4

Instance  Vlans mapped
--------  ---------------------------------------------------------------------
0         1-4,6,11-21,23-42,44-57,59-66,68-78,80-145,147-4094
1         5,7-10
2         22,43,58,67,79
3         146
-------------------------------------------------------------------------------
Rack15SW1#

root bridgeの制御

設定投入

SW1をinstance0, 2のroot bridgeとし、SW3をinstance1,3のroot bridgeとします。

 [SW1]
spanning-tree mst 0,2 priority 0

 [SW3]
spanning-tree mst 1,3 priority 0

動作確認

SW1, SW3がそれぞれroot bridgeになっている事を確認します。

 [SW1]
Rack15SW1#show spanning-tree

MST0
  Spanning tree enabled protocol mstp
  Root ID    Priority    0
             Address     001e.bee7.0880
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    0      (priority 0 sys-id-ext 0)
             Address     001e.bee7.0880
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1               Desg FWD 200000    128.3    P2p
Fa0/5               Desg FWD 200000    128.7    P2p
Fa0/13              Desg FWD 200000    128.15   P2p
Fa0/14              Desg FWD 200000    128.16   P2p
Fa0/15              Desg FWD 200000    128.17   P2p
Fa0/19              Desg FWD 200000    128.21   P2p
Fa0/20              Desg LRN 200000    128.22   P2p Dispute
Fa0/21              Desg LRN 200000    128.23   P2p Dispute


MST1
  Spanning tree enabled protocol mstp
  Root ID    Priority    1
             Address     000f.9084.e580
             Cost        400000
             Port        21 (FastEthernet0/19)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
             Address     001e.bee7.0880
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/13              Altn BLK 200000    128.15   P2p
Fa0/14              Altn BLK 200000    128.16   P2p
Fa0/15              Altn BLK 200000    128.17   P2p
Fa0/19              Root FWD 200000    128.21   P2p
Fa0/20              Altn BLK 200000    128.22   P2p
Fa0/21              Altn BLK 200000    128.23   P2p


MST2
  Spanning tree enabled protocol mstp
  Root ID    Priority    2
             Address     001e.bee7.0880
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    2      (priority 0 sys-id-ext 2)
             Address     001e.bee7.0880
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

 <omitted>

 [SW3]
Rack15SW3#show spanning-tree

MST0
  Spanning tree enabled protocol mstp
  Root ID    Priority    0
             Address     001e.bee7.0880
             Cost        0
             Port        19 (FastEthernet0/19)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32768  (priority 32768 sys-id-ext 0)
             Address     000f.9084.e580
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/5               Desg FWD 200000    128.5    P2p Edge
Fa0/16              Altn BLK 200000    128.16   P2p
Fa0/17              Altn BLK 200000    128.17   P2p
Fa0/18              Altn BLK 200000    128.18   P2p
Fa0/19              Root FWD 200000    128.19   P2p
Fa0/20              Altn BLK 200000    128.20   P2p
Fa0/21              Altn BLK 200000    128.21   P2p
Fa0/24              Desg FWD 2000000   128.24   Shr Edge


MST1
  Spanning tree enabled protocol mstp
  Root ID    Priority    1
             Address     000f.9084.e580
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    1      (priority 0 sys-id-ext 1)
             Address     000f.9084.e580
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

 <omitted>

root portの制御

設定投入 cost

MST instance 2について、SW4からSW1へのトラフィックがSW4, SW3, SW2, SW1と遠回りするようにcostを設定します。

 [SW4]
interface range FastEthernet 0/13-15
 spanning-tree mst 2 cost 700000

動作確認 cost

MST instance 2について、SW4からSW1へのトラフィックが遠回りするようになっている事を確認します。

 [SW4]
Rack15SW4#show spanning-tree mst 2

##### MST2    vlans mapped:   22,43,58,67,79
Bridge        address 000f.9095.6600  priority      32770 (32768 sysid 2)
Root          address 001e.bee7.0880  priority      2     (0 sysid 2)
              port    Fa0/19          cost          600000    rem hops 17

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/13           Altn BLK 700000    128.13   P2p
Fa0/14           Altn BLK 700000    128.14   P2p
Fa0/15           Altn BLK 700000    128.15   P2p
Fa0/19           Root FWD 200000    128.19   P2p
Fa0/20           Altn BLK 200000    128.20   P2p
Fa0/21           Altn BLK 200000    128.21   P2p

Rack15SW4#

設定投入 port priority

MST instance 2について、SW4からSW1のトラフィックがSW4 Fa0/21を使用するように設定します。SW4 Fa0/21がlink downした時は、SW4 Fa0/20を使用するように設定します。

 [SW3]
interface FastEthernet 0/21
 spanning-tree mst 2 port-priority 16
interface FastEthernet 0/20
 spanning-tree mst 2 port-priority 32

動作確認 port priority

SW3のport priorityが変わった事と、SW4のRoot Portが変わった事を確認します。

 [SW3]
Rack15SW3#show spanning-tree mst 2

##### MST2    vlans mapped:   22,43,58,67,79
Bridge        address 000f.9084.e580  priority      32770 (32768 sysid 2)
Root          address 001e.bee7.0880  priority      2     (0 sysid 2)
              port    Fa0/16          cost          400000    rem hops 18

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/16           Root FWD 200000    128.16   P2p
Fa0/17           Altn BLK 200000    128.17   P2p
Fa0/18           Altn BLK 200000    128.18   P2p
Fa0/19           Desg FWD 200000    128.19   P2p
Fa0/20           Desg FWD 200000     32.20   P2p
Fa0/21           Desg FWD 200000     16.21   P2p
Fa0/24           Desg FWD 2000000   128.24   Shr Edge

Rack15SW3#

 [SW4]
Rack15SW4#show spanning-tree mst 2

##### MST2    vlans mapped:   22,43,58,67,79
Bridge        address 000f.9095.6600  priority      32770 (32768 sysid 2)
Root          address 001e.bee7.0880  priority      2     (0 sysid 2)
              port    Fa0/21          cost          600000    rem hops 17

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/13           Altn BLK 700000    128.13   P2p
Fa0/14           Altn BLK 700000    128.14   P2p
Fa0/15           Altn BLK 700000    128.15   P2p
Fa0/19           Altn BLK 200000    128.19   P2p
Fa0/20           Altn BLK 200000    128.20   P2p
Fa0/21           Root FWD 200000    128.21   P2p

Rack15SW4#

timer

設定投入

以下のコマンドを投入し、spanning-treeに関するtimerを変更します。

 [SW1, SW2, SW3, SW4]
spanning-tree mst hello-time 1
spanning-tree mst max-age 10
spanning-tree mst forward-time 7

動作確認

showコマンドよりtimerが変わった事を確認します。

 [SW1]
Rack15SW1#show spanning-tree

MST0
  Spanning tree enabled protocol mstp
  Root ID    Priority    0
             Address     001e.bee7.0880
             This bridge is the root
             Hello Time   1 sec  Max Age 10 sec  Forward Delay  7 sec

  Bridge ID  Priority    0      (priority 0 sys-id-ext 0)
             Address     001e.bee7.0880
             Hello Time   1 sec  Max Age 10 sec  Forward Delay  7 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1               Desg FWD 200000    128.3    P2p
Fa0/5               Desg FWD 200000    128.7    P2p
Fa0/13              Desg FWD 200000    128.15   P2p
Fa0/14              Desg FWD 200000    128.16   P2p
Fa0/15              Desg FWD 200000    128.17   P2p

 <omitted>

Tips

rapid PVSTからMSTへの移行

rapid PVSTとMSTが混在している環境では、一部のポートがPVST互換モードで動作します。但し、PVST互換モードが正常に機能するのは、Root BridgeがMST domainに存在する場合のみです。MSTに移行するにあたり、rapid PVSTからMSTへの一括移行が難しい場合は、MST domainにRoot Bridgeが配置されるように計画して下さい。

それでは、rapid PVSTとMSTの混在環境について動作確認を行います。SW1をrapid PVSTに変更し、SW1がRoot Bridgeになるようにします。また、検証の都合上、range f0/20-21をshutdownさせます。

 [SW1]
spanning-tree mode rapid-pvst
spanning-tree vlan 1-4094 priority 0
!
interface range FastEthernet 0/20-21
 shutdown

SW4を確認すると、f0/13がPVST_Incという状態になり疎通不能になっている事が読み取れます。

 [SW4]
Rack5SW4#show spanning-tree mst 2

##### MST2    vlans mapped:   22,43,58,67,79
Bridge        address 000f.f759.b000  priority      32770 (32768 sysid 2)
Root          address 000d.6520.8580  priority      32770 (32768 sysid 2)
              port    Fa0/21          cost          200000    rem hops 19

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/13           Mstr BKN*700000    128.13   P2p Bound(PVST) *PVST_Inc
Fa0/19           Altn BLK 200000    128.19   P2p
Fa0/20           Altn BLK 200000    128.20   P2p
Fa0/21           Root FWD 200000    128.21   P2p

Rack5SW4#

Root BridgeがMST domainに配置されるよう、SW1のpriorityを大きくします。

 [SW1]
spanning-tree vlan 1-4094 priority 61440

しばらくすると、PVST_Incが解消された事が読み取れます。

 [SW4]
Rack5SW4#
*Mar  1 00:07:57.255: %SPANTREE-2-PVSTSIM_OK: PVST Simulation i
Rack5SW4#
Rack5SW4#
Rack5SW4#show spanning-tree mst 2

##### MST2    vlans mapped:   22,43,58,67,79
Bridge        address 000f.f759.b000  priority      32770 (32768 sysid 2)
Root          address 000d.6520.8580  priority      32770 (32768 sysid 2)
              port    Fa0/21          cost          200000    rem hops 19

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/13           Desg FWD 700000    128.13   P2p Bound(PVST)
Fa0/19           Altn BLK 200000    128.19   P2p
Fa0/20           Altn BLK 200000    128.20   P2p
Fa0/21           Root FWD 200000    128.21   P2p

Rack5SW4#
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