Spanning-Tree Blocking Vlan

[heheho]

Hello, I'm facing issue to block all the VLANS in Port g0/2 for Switch1. I changed the root primary for each VLAN then i got to block those, but VLAN 56 cannot be blocked. I tried changing the cost, the priority still not blocking VLAN 56. I am not sure which part I have done wrong.  🥺

SWITCH>EN

SWITCH#SH SPAN INT G0/1

VLAN ROLE STS COST PRIO.NBR TYPE

---------------- ---- --- --------- -------- --------------------------------

VLAN0001 ROOT FWD 4 128.25 P2P

VLAN0002 ROOT FWD 4 128.25 P2P

VLAN0003 ROOT FWD 4 128.25 P2P

VLAN0004 ROOT FWD 4 128.25 P2P

VLAN0005 ROOT FWD 4 128.25 P2P

VLAN0006 ROOT FWD 4 128.25 P2P

VLAN0016 ROOT FWD 4 128.25 P2P

VLAN0025 ROOT FWD 4 128.25 P2P

VLAN0035 ROOT FWD 4 128.25 P2P

VLAN0046 ROOT FWD 4 128.25 P2P

VLAN0056 DESG FWD 4 128.25 P2P

SWITCH#SH SPAN INT G0/2

VLAN ROLE STS COST PRIO.NBR TYPE

---------------- ---- --- --------- -------- --------------------------------

VLAN0001 ALTN BLK 4 128.26 P2P

VLAN0002 ALTN BLK 10000000 128.26 P2P

VLAN0003 ALTN BLK 4 128.26 P2P

VLAN0004 ALTN BLK 4 128.26 P2P

VLAN0005 ALTN BLK 4 128.26 P2P

VLAN0006 ALTN BLK 4 128.26 P2P

VLAN0016 ALTN BLK 4 128.26 P2P

VLAN0025 ALTN BLK 4 128.26 P2P

VLAN0035 ALTN BLK 4 128.26 P2P

VLAN0046 ALTN BLK 4 128.26 P2P

VLAN0056 DESG FWD 50000000 128.26 P2P

[liviu.gheorghe]

Can you share a picture of your topology containing port numbers for the connected switches?

[heheho]

here is the topology

[liviu.gheorghe]

The spanning tree protocol transitions ports in the blocking state in order to break loops in the switch topology.

From what I'm seeing from your picture - there isn't a loop in your topology, so no ports will be blocked by the spanning tree protocol.

HTH

[anonymoushe]

.

[heheho]

Is it because the VLAN 56 is not in the bottom part of the topology like connected with another switch so no blocking happens? Coz my other VLAN can be blocked, except for VLAN 56. 

[MHM Cisco World]

What I think you have misconfig of port channel

That explains issue, 

Mr @liviu.gheorghe can help you with this

MHM

[liviu.gheorghe]

Can you share your PacketTracer file?

[heheho]

.

[liviu.gheorghe]

That is correct. Because on the bottom switch there is no vlan 56 defined, there is no loop between the switches Gigabit 0/1 and Gigabit 0/2 interfaces, so no interfaces are in blocking state on the top switch for vlan 56:

Switch#sho spanning-tree vlan 56

VLAN0056

Spanning tree enabled protocol ieee

Root ID Priority 61496

Address 0003.E457.98C5

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 61496 (priority 61440 sys-id-ext 56)

Address 0003.E457.98C5

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/20 Desg FWD 100 128.20 P2p

Fa0/24 Desg FWD 100 128.24 P2p

Gi0/1 Desg FWD 4 128.25 P2p

Gi0/2 Desg FWD 50000000 128.26 P2p

For the other vlans that are defined in both top and bottom switches, one of the Gigabit ports between the switches will be put in blocking by spanning tree protocol to prevent a loop:

Switch#sho spanning-tree vlan 1

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 20481

Address 00D0.97C1.BE9B

Cost 4

Port 25(GigabitEthernet0/1)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)

Address 0003.E457.98C5

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/2 Desg FWD 19 128.2 P2p

Gi0/1 Root FWD 4 128.25 P2p

Gi0/2 Altn BLK 4 128.26 P2p

Fa0/1 Desg FWD 19 128.1 P2p

HTH

[heheho]

Got it, but the instruction requires us to make the int g0/2 in switch 1 to be blocked for all VLANs, that's why I wonder why VLAN 56 cannot be blocked. Perhaps is there any other method can make the VLAN 56 to be blocked? Other than adding new VLAN 56 in the bottom switch part?🥺 Coz in switch 1, I do have 2 interfaces,  int g0/1 and int g0/2, so can use int g0/1 then block int g0/2?

[liviu.gheorghe]

There are two possibilities - either the instructions are wrong or we are not understanding them correctly.

Can you send me the all instructions to have a look?

[liviu.gheorghe]

Can you send also the design and implementation instructions?

[heheho]

the below is my lab1, so i just the flw the connection from router to router to be implemented in this exercise

R1 to R2 R3 R6

R2 to R1 R5 R4

R3 to R1 R5

R4 to R2 R6

R5 to R2 R3 R6

R6 to R1 R4 R5

[heheho]

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