I have two 3550 12G as core layer linked together with a 3 agregate ports channel, and several 2950 (as distrib layer)witch have each 2 giga redondant link on each 3550. I have configured (?) spanning tree, when I disconnect one link sometimes it works and the 2nd redundant link comes up, sometimes it never comes up.
When I debug the spanning tree, sometimes I see the giga interface in Blocked and forward state as it should be and sometimes i dont see any state .
config 3550 :
Building configuration...
Current configuration : 2131 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname 3550A
!
enable secret -----
enable password -----
!
ip subnet-zero
!
!
!
spanning-tree extend system-id
spanning-tree vlan 1 priority 8192
!
!
!
interface Port-channel1
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
!
interface GigabitEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
!
interface GigabitEthernet0/2
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
!
interface GigabitEthernet0/3
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
!
interface GigabitEthernet0/4
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
!
interface GigabitEthernet0/5
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
!
interface GigabitEthernet0/6
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
!
interface GigabitEthernet0/7
description Channel
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
channel-group 1 mode on
!
interface GigabitEthernet0/8
description Channel
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
channel-group 1 mode on
!
interface GigabitEthernet0/9
description Channel
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
channel-group 1 mode on
!
interface GigabitEthernet0/10
no ip address
!
interface GigabitEthernet0/11
no ip address
!
interface GigabitEthernet0/12
no ip address
!
interface Vlan1
ip address x.y.z.w 255.255.255.0
!
ip classless
ip http server
!
!
!
!
line con 0
line vty 0 4
password -----
login
line vty 5 15
password -----
login
!
end
config 2950 :
Current configuration : 1585 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname 29501
!
enable secret ------
enable password ----
!
ip subnet-zero
!
!
spanning-tree extend system-id
spanning-tree uplinkfast
!
!
interface FastEthernet0/1
no ip address
spanning-tree portfast
!
interface FastEthernet0/2
switchport mode access
no ip address
spanning-tree portfast
!
interface FastEthernet0/3
switchport mode access
no ip address
spanning-tree portfast
!
interface FastEthernet0/4
no ip address
spanning-tree portfast
!
interface FastEthernet0/5
switchport mode access
no ip address
spanning-tree portfast
!
interface FastEthernet0/6
no ip address
spanning-tree portfast
!
interface FastEthernet0/7
no ip address
spanning-tree portfast
!
interface FastEthernet0/8
no ip address
spanning-tree portfast
!
interface FastEthernet0/9
no ip address
spanning-tree portfast
!
interface FastEthernet0/10
no ip address
spanning-tree portfast
!
interface FastEthernet0/11
no ip address
spanning-tree portfast
!
interface FastEthernet0/12
no ip address
spanning-tree portfast
!
interface GigabitEthernet0/1
description link 3550A
switchport mode trunk
no ip address
!
interface GigabitEthernet0/2
description link 3550B
switchport mode trunk
no ip address
!
interface Vlan1
ip address x.y.z.t 255.255.255.0
no ip route-cache
!
ip http server
!
!
line con 0
line vty 0 4
password ----
login
line vty 5 15
password ----
login
!
end
