08-04-2008 02:07 AM - edited 03-07-2019 12:29 AM
Hi, I have a problem with spanning-tree protocol on two interface on 2801.
Two interface in bridge are connected on the same switch but are all two in forwarding state.
My conf:
interface FastEthernet0/0
description nn
no ip address
duplex auto
speed auto
!
interface FastEthernet0/0.1
description LAN_STI_if1
encapsulation dot1Q 1 native
bridge-group 1
bridge-group 1 path-cost 150
bridge-group 1 priority 16
!
interface FastEthernet0/0.2
description SGRT_if1
encapsulation dot1Q 2
bridge-group 2
bridge-group 2 path-cost 150
bridge-group 2 priority 16
!
interface FastEthernet0/0.3
description SCC_if1
encapsulation dot1Q 3
bridge-group 3
bridge-group 3 path-cost 150
bridge-group 3 priority 16
!
interface FastEthernet0/1
no ip address
duplex auto
speed auto
!
interface FastEthernet0/1.1
description LAN_STI_if2
encapsulation dot1Q 1 native
bridge-group 1
bridge-group 1 path-cost 100
bridge-group 1 priority 8
!
interface FastEthernet0/1.2
description SGRT_if2
encapsulation dot1Q 2
bridge-group 2
bridge-group 2 path-cost 100
bridge-group 2 priority 8
!
interface FastEthernet0/1.3
description SCC_if2
encapsulation dot1Q 3
bridge-group 3
bridge-group 3 path-cost 100
bridge-group 3 priority 8
!
bridge 1 protocol ieee
bridge 1 route ip
bridge 2 protocol ieee
bridge 2 route ip
bridge 3 protocol ieee
bridge 3 route ip
Now the log of sh spanning-tree:
gw-boav-002#sh spAnning-tree 3
Bridge group 3 is executing the ieee compatible Spanning Tree protocol
Bridge Identifier has priority 32768, address 0000.0c4b.c400
Configured hello time 2, max age 20, forward delay 15
We are the root of the spanning tree
Topology change flag not set, detected flag not set
Number of topology changes 11 last change occurred 00:38:06 ago
from FastEthernet0/0.3
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 0, notification 0, aging 300
Port 40 (FastEthernet0/0.3) of Bridge group 3 is forwarding
Port path cost 150, Port priority 16, Port Identifier 16.40.
Designated root has priority 32768, address 0000.0c4b.c400
Designated bridge has priority 32768, address 0000.0c4b.c400
Designated port id is 16.40, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 253064, received 66
Port 43 (FastEthernet0/1.3) of Bridge group 3 is forwarding
Port path cost 100, Port priority 8, Port Identifier 8.43.
Designated root has priority 32768, address 0000.0c4b.c400
Designated bridge has priority 32768, address 0000.0c4b.c400
Designated port id is 8.43, designated path cost 0
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 171659, received 42
gw-boav-002#
In attach all log of sh spanning-tree, as you can see other if are in blocking state correctly.
Anyone have some ideas?
Thanks Enrico.
Solved! Go to Solution.
08-04-2008 02:22 AM
Hi,
The reason both ports are forwarding is because;
"We are the root of the spanning tree "
Your router is the STP root for vlan 3, whereas vlans 1 & 2, are using an external STP root, as shown by
"Current root has priority 24578, address 001e.132b.6080"
So whatever device this is, probably the switch that the router is connected to either has its STP root for vlan3 higher than the router does, or perhaps doesnt even have vlan 3 configured.
Check the STP for vlan 3 on the device upstream from router.
HTH
LR
08-04-2008 02:22 AM
Hi,
The reason both ports are forwarding is because;
"We are the root of the spanning tree "
Your router is the STP root for vlan 3, whereas vlans 1 & 2, are using an external STP root, as shown by
"Current root has priority 24578, address 001e.132b.6080"
So whatever device this is, probably the switch that the router is connected to either has its STP root for vlan3 higher than the router does, or perhaps doesnt even have vlan 3 configured.
Check the STP for vlan 3 on the device upstream from router.
HTH
LR
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