03-14-2010 12:23 AM - edited 03-06-2019 10:07 AM
Hi all,
My question is i have 2 2950t switches and when i do this
1> connect port from switch A to switch B with crossover cable and config them as
config t
switchport mode access
spanning tree portfast
then Switch A port has Amber light while it is in blocking state
2>connect port from switch A to switch B with crossover cable and config them as trunk port only
then Switch A port has green light and it is in blocking state.
My question is why blocking port has green light instead of Amber
thanks
mahesh
Solved! Go to Solution.
03-14-2010 04:21 PM
Mahesh
It's what i was saying. Once you configure fa0/8 as a trunk link on vlan 1 it is still blocking but for vlan 30 -
VLAN0030
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0003.6b7b.5a01
Cost 22
Port 65 (Port-channel1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32798 (priority 32768 sys-id-ext 30)
Address 000b.bece.bbc0
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 1000
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/8 Desg FWD 19 128.8 P2p**********************************
Po1 Root FWD 3 128.65 P2p
You can see that fa0/8 is forwarding for vlan 30. This is why the port is green when you configure it as a trunk because it blocks on vlan 1 but it forwards on vlan 30 so the port shows as forwarding. Remember that each vlan runs it's own STP instance.
Jon
03-14-2010 12:41 AM
mahesh18 wrote:
Hi all,
My question is i have 2 2950t switches and when i do this
1> connect port from switch A to switch B with crossover cable and config them as
config t
switchport mode access
spanning tree portfast
then Switch A port has Amber light while it is in blocking state
2>connect port from switch A to switch B with crossover cable and config them as trunk port only
then Switch A port has green light and it is in blocking state.
My question is why blocking port has green light instead of Amber
thanks
mahesh
Mahesh
If the connection is blocking presumably the switches are already connected with an existing link ?
As for the amber/green lights. Remember that STP is per vlan on Cisco switches so when it is configured as an access port it could well block on that vlan. With the port configured as a trunk port the same vlan may be blocked but other vlans may well be forwarding. Can you check whether all the vlans allowed on the trunk are blocked.
Jon
03-14-2010 12:56 AM
Hi jon
Here is info from switch A
950T#sh spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0003.6b7b.5a00
Cost 22
Port 65 (Port-channel1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 000b.bece.bbc0
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 1000
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/8 Altn BLK 19 128.8 P2p**********************
Fa0/9 Desg FWD 19 128.9 Edge P2p
Fa0/16 Desg FWD 19 128.16 Edge P2p
Fa0/19 Desg FWD 19 128.19 Edge P2p
Po1 Root FWD 3 128.65 P2p
VLAN0030
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0003.6b7b.5a01
Cost 22
Port 65 (Port-channel1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32798 (priority 32768 sys-id-ext 30)
Address 000b.bece.bbc0
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 1000
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1 Root FWD 3 128.65 P2p
Here is config of port fa0/8 port from switch A
2950T#sh run int fa0/8
Building configuration...
Current configuration : 144 bytes
!
interface FastEthernet0/8
description Connection to 2950T2 Switch with cross over wire.
switchport mode access
spanning-tree portfast
end
Please explain me in more detail what you mention
thanks
03-14-2010 06:45 AM
Mahesh
Can you configure fa0/8 as a trunk and then post the output of "sh spanning-tree" ?
Jon
03-14-2010 03:18 PM
Hi Jon,
On switch A which has amer light for port fa0/8 i config that as trunk
2950T#sh run int fa0/8
Building configuration...
Current configuration : 119 bytes
!
interface FastEthernet0/8
description Connection to 2950T2 Switch with cross over wire.
switchport mode trunk
end
2950T#sh spann
2950T#sh spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0003.6b7b.5a00
Cost 22
Port 65 (Port-channel1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 000b.bece.bbc0
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 1000
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/8 Altn BLK 19 128.8 P2p**********************************************
Fa0/9 Desg FWD 19 128.9 Edge P2p
Fa0/16 Desg FWD 19 128.16 Edge P2p
Fa0/19 Desg FWD 19 128.19 Edge P2p
Po1 Root FWD 3 128.65 P2p
VLAN0030
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0003.6b7b.5a01
Cost 22
Port 65 (Port-channel1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32798 (priority 32768 sys-id-ext 30)
Address 000b.bece.bbc0
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 1000
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/8 Desg FWD 19 128.8 P2p**********************************
Po1 Root FWD 3 128.65 P2p
Now the port fa0/8 on switch A has green light and other nei switch B port fa0/8 has also green light.
Switch B port fa0/8 config and spanning tree output
950T2# sh run int fa0/8
Building configuration...
Current configuration : 143 bytes
!
interface FastEthernet0/8
description Connection to 2950T Switch with cross over wire.
switchport mode access
spanning-tree portfast
end
2950T2#sh spann
2950T2#sh spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0003.6b7b.5a00
Cost 19
Port 15 (FastEthernet0/15)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 000d.65de.ff40
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 1000
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/8 Desg FWD 19 128.8 P2p
Fa0/15 Root FWD 19 128.15 P2p Peer(STP)
Fa0/16 Altn BLK 19 128.16 P2p Peer(STP)
Po1 Desg FWD 3 128.65 P2p
VLAN0030
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0003.6b7b.5a01
Cost 19
Port 15 (FastEthernet0/15)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32798 (priority 32768 sys-id-ext 30)
Address 000d.65de.ff40
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 1000
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/15 Root FWD 19 128.15 P2p Peer(STP)
Fa0/16 Altn BLK 19 128.16 P2p Peer(STP)
Po1 Desg FWD 3 128.65 P2p
Thanks
03-14-2010 04:21 PM
Mahesh
It's what i was saying. Once you configure fa0/8 as a trunk link on vlan 1 it is still blocking but for vlan 30 -
VLAN0030
Spanning tree enabled protocol rstp
Root ID Priority 32768
Address 0003.6b7b.5a01
Cost 22
Port 65 (Port-channel1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32798 (priority 32768 sys-id-ext 30)
Address 000b.bece.bbc0
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 1000
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/8 Desg FWD 19 128.8 P2p**********************************
Po1 Root FWD 3 128.65 P2p
You can see that fa0/8 is forwarding for vlan 30. This is why the port is green when you configure it as a trunk because it blocks on vlan 1 but it forwards on vlan 30 so the port shows as forwarding. Remember that each vlan runs it's own STP instance.
Jon
03-14-2010 07:00 PM
Hi jon,
thanks once again for your explanation.
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