На обоих свичах конфигурация
Глобально включить MST и зайти в режим настройки MST выполнив команду
spanning-tree mode mst
spanning-tree extend system-id
spanning-tree mst configuration
name MST (Имя региона MST)
revision 1 (MST revision number)
instance 1 vlan 1-99, 200-299, 400-499, 600-699, 800-899, 1000-1099, 1200-1299
instance 1 vlan 1400-1499, 1600-1699, 1800-1899, 2000-2099, 2200-2299
instance 1 vlan 2400-2499, 2600-2699, 2800-2899, 3000-3099, 3200-3299
instance 1 vlan 3400-3499, 3600-3699, 3800-3899, 4000-4094
instance 2 vlan 100-199, 300-399, 500-599, 700-799, 900-999, 1100-1199
instance 2 vlan 1300-1399, 1500-1599, 1700-1799, 1900-1999, 2100-2199
instance 2 vlan 2300-2399, 2500-2599, 2700-2799, 2900-2999, 3100-3199
instance 2 vlan 3300-3399, 3500-3599, 3700-3799, 3900-3999
как видим создали 2 MST instance для балансировки вланов по портам, чтобы оба порта работали. Теперь конфигурация интерфейсов
interface GigabitEthernet1/0/1
description ODF-2
switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate
speed nonegotiate
spanning-tree link-type point-to-point
spanning-tree mst 1 port-priority 112
spanning-tree mst 2 port-priority 144
end
interface GigabitEthernet1/0/2
description ODF-3
switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate
speed nonegotiate
spanning-tree link-type point-to-point
spanning-tree mst 1 port-priority 144
spanning-tree mst 2 port-priority 112
Как видим разные MST instance имет разные приоритеты на портах - причину смотрим выше.
Объяснение еще одной команды
spanning-tree link-type {point-to-point | shared}
no spanning-tree link-type
Syntax Description
point-to-point
Specify that the link type of an interface is point-to-point.
shared
Specify that the link type of an interface is shared.
Defaults
The switch derives the link type of an interface from the duplex mode. A full-duplex interface is considered a point-to-point link, and a half-duplex interface is considered a shared link.
()
Увидеть это также можно вот так
#show spanning-tree interface gi 1/0/1 detail
Port 1 (GigabitEthernet1/0/1) of MST00 is designated forwarding
Port path cost 20000, Port priority 128, Port Identifier 128.1.
Designated root has priority 32768, address 001b.0c51.7580
Designated bridge has priority 32768, address 001b.0c51.7580
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: 4
Link type is point-to-point, Internal
Bpdu filter is enabled internally
BPDU: sent 12217849, received 905090
Port 1 (GigabitEthernet1/0/1) of MST01 is designated forwarding
Port path cost 20000, Port priority 112, Port Identifier 112.1.
Designated root has priority 32769, address 001b.0c51.7580
Designated bridge has priority 32769, address 001b.0c51.7580
Designated port id is 112.1, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 4
Link type is point-to-point, Internal
Bpdu filter is enabled internally
BPDU: sent 12217849, received 905090
Port 1 (GigabitEthernet1/0/1) of MST02 is designated forwarding
Port path cost 20000, Port priority 144, Port Identifier 144.1.
Designated root has priority 32770, address 001b.0c51.7580
Designated bridge has priority 32770, address 001b.0c51.7580
Designated port id is 144.1, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 3
Link type is point-to-point, Internal
Bpdu filter is enabled internally
BPDU: sent 12217849, received 905090
#show spanning-tree summary
Switch is in mst mode
Root bridge for: MST00-MST02
Extended system ID is enabled
Portfast Default is disabled
PortFast BPDU Guard Default is disabled
Portfast BPDU Filter Default is disabled
Loopguard Default is disabled
EtherChannel misconfig guard is enabled
UplinkFast is disabled
BackboneFast is disabled
Configured Pathcost method used is short (Operational value is long)
Name Blocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
MST00 0 0 0 8 8
MST01 0 0 0 7 7
MST02 0 0 0 6 6
---------------------- -------- --------- -------- ---------- ----------
3 msts 0 0 0 21 21
На другом свиче все аналогично только в конфиге свича добавлена одна строка
interface GigabitEthernet1/0/2
description ODF-3
switchport trunk encapsulation dot1q
switchport mode trunk
speed nonegotiate
spanning-tree link-type point-to-point
spanning-tree mst pre-standard
spanning-tree mst 1 port-priority 144
spanning-tree mst 2 port-priority 112
When you connect the prestandard MST switch with the standard MST switch, you need to configure spanning-tree mst pre-standard in the interface of the standard MST switch.
Catalyst 3550/3560/3750: TheMST implementation in Cisco IOS Release 12.2(25)SEC is based on the IEEE 802.1s standard. The MST implementations in earlier Cisco IOS releases are prestandard.
То есть если у вас версия => 12.2(25)SEC то эта командочка не нужна.
Все это также можно посмотреть если заюзать команду
#show spanning-tree mst
###### MST00 vlans mapped: none
Bridge address 001b.0c51.7580 priority 32768 (32768 sysid 0)
Root this switch for CST and IST
Configured hello time 2, forward delay 15, max age 20, max hops 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi1/0/1 Desg FWD 20000 128.1 P2p
Gi1/0/2 Desg FWD 20000 128.2 P2p
Fa1/0/1 Desg FWD 200000 128.3 P2p Bound(PVST)
Fa1/0/3 Desg FWD 200000 128.5 Shr
Fa1/0/6 Desg FWD 200000 128.8 P2p
Fa1/0/22 Desg FWD 200000 128.24 P2p
Fa1/0/23 Desg FWD 200000 128.25 P2p
Fa1/0/24 Desg FWD 200000 128.26 P2p
###### MST01 vlans mapped: 1-99,200-299,400-499,600-699,800-899
1000-1099,1200-1299,1400-1499,1600-1699
1800-1899,2000-2099,2200-2299,2400-2499
2600-2699,2800-2899,3000-3099,3200-3299
3400-3499,3600-3699,3800-3899,4000-4094
Bridge address 001b.0c51.7580 priority 32769 (32768 sysid 1)
Root this switch for MST01
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi1/0/1 Desg FWD 20000 112.1 P2p
Gi1/0/2 Desg FWD 20000 144.2 P2p
Fa1/0/1 Boun FWD 200000 128.3 P2p Bound(PVST)
Fa1/0/3 Desg FWD 200000 128.5 Shr
Fa1/0/6 Desg FWD 200000 128.8 P2p
Fa1/0/23 Desg FWD 200000 128.25 P2p
Fa1/0/24 Desg FWD 200000 128.26 P2p
###### MST02 vlans mapped: 100-199,300-399,500-599,700-799,900-999
1100-1199,1300-1399,1500-1599,1700-1799
1900-1999,2100-2199,2300-2399,2500-2599
2700-2799,2900-2999,3100-3199,3300-3399
3500-3599,3700-3799,3900-3999
Bridge address 001b.0c51.7580 priority 32770 (32768 sysid 2)
Root this switch for MST02
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi1/0/1 Desg FWD 20000 144.1 P2p
Gi1/0/2 Desg FWD 20000 112.2 P2p
Fa1/0/1 Boun FWD 200000 128.3 P2p Bound(PVST)
Fa1/0/3 Desg FWD 200000 128.5 Shr
Fa1/0/22 Desg FWD 200000 128.24 P2p
Fa1/0/24 Desg FWD 200000 128.26 P2p
