Solved: Re: Spanning-Tree Blocked Switch Port Locations (Unable to Block) - Page 2

Outdoor Adventurer · ‎12-08-2022

I have (3) switches which are connected together in a redundant configuration. The connection between the SludgeBLDG and DigestBLDG switches are using ports Gig1/0/3-4. I have manually set the port cost for all VLANs to 100 but am still unable to configure the connections between the switches to block. Essentially, I am trying to force the switches to use a different RSTP path.

My switch configurations are below.

************************************

SludgeBldg3850#sh spanning-tree

VLAN0001

Spanning tree enabled protocol rstp

Root ID Priority 32769

Address

Cost 4

Port 1(GigabitEthernet1/0/1)

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

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/3 Desg FWD 100 128.3 P2p

Gi1/0/1 Root FWD 4 128.1 P2p

Gi1/0/2 Altn BLK 4 128.2 P2p

Gi1/0/4 Altn BLK 100 128.4 P2p

VLAN0099

Spanning tree enabled protocol rstp

Root ID Priority 32867

Address

Cost 4

Port 1(GigabitEthernet1/0/1)

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

Bridge ID Priority 32867 (priority 32768 sys-id-ext 99)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/3 Desg FWD 100 128.3 P2p

Gi1/0/1 Root FWD 4 128.1 P2p

Gi1/0/2 Altn BLK 4 128.2 P2p

Gi1/0/4 Desg FWD 100 128.4 P2p

VLAN0100

Spanning tree enabled protocol rstp

Root ID Priority 32868

Address

Cost 4

Port 1(GigabitEthernet1/0/1)

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

Bridge ID Priority 32868 (priority 32768 sys-id-ext 100)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/3 Desg FWD 100 128.3 P2p

Gi1/0/1 Root FWD 4 128.1 P2p

Gi1/0/2 Altn BLK 4 128.2 P2p

Gi1/0/4 Altn BLK 100 128.4 P2p

VLAN0105

Spanning tree enabled protocol rstp

Root ID Priority 32873

Address

Cost 4

Port 1(GigabitEthernet1/0/1)

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

Bridge ID Priority 32873 (priority 32768 sys-id-ext 105)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/3 Desg FWD 100 128.3 P2p

Gi1/0/1 Root FWD 4 128.1 P2p

Gi1/0/2 Altn BLK 4 128.2 P2p

Gi1/0/4 Altn BLK 100 128.4 P2p

VLAN0215

Spanning tree enabled protocol rstp

Root ID Priority 32983

Address

Cost 4

Port 1(GigabitEthernet1/0/1)

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

Bridge ID Priority 32983 (priority 32768 sys-id-ext 215)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/3 Desg FWD 100 128.3 P2p

Gi1/0/1 Root FWD 4 128.1 P2p

Gi1/0/2 Altn BLK 4 128.2 P2p

Gi1/0/4 Altn BLK 100 128.4 P2p

VLAN0220

Spanning tree enabled protocol rstp

Root ID Priority 32988

Address

Cost 4

Port 1(GigabitEthernet1/0/1)

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

Bridge ID Priority 32988 (priority 32768 sys-id-ext 220)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/3 Desg FWD 100 128.3 P2p

Gi1/0/1 Root FWD 4 128.1 P2p

Gi1/0/2 Altn BLK 4 128.2 P2p

Gi1/0/4 Desg FWD 100 128.4 P2p

******************************************************************

DigestBldg3850#sh spanning-tree

VLAN0001

Spanning tree enabled protocol rstp

Root ID Priority 32769

Address

Cost 4

Port 5(GigabitEthernet1/0/5)

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

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/6 Altn BLK 4 128.6 P2p

Gi1/0/3 Altn BLK 4 128.3 P2p

Gi1/0/4 Desg FWD 4 128.4 P2p

Gi1/0/5 Root FWD 4 128.5 P2p

VLAN0099

Spanning tree enabled protocol rstp

Root ID Priority 32867

Address

Cost 4

Port 5(GigabitEthernet1/0/5)

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

Bridge ID Priority 32867 (priority 32768 sys-id-ext 99)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/6 Altn BLK 4 128.6 P2p

Gi1/0/3 Altn BLK 4 128.3 P2p

Gi1/0/4 Altn BLK 4 128.4 P2p

Gi1/0/5 Root FWD 4 128.5 P2p

VLAN0100

Spanning tree enabled protocol rstp

Root ID Priority 32868

Address

Cost 4

Port 5(GigabitEthernet1/0/5)

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

Bridge ID Priority 32868 (priority 32768 sys-id-ext 100)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/6 Altn BLK 4 128.6 P2p

Gi1/0/3 Altn BLK 100 128.3 P2p

Gi1/0/4 Desg FWD 100 128.4 P2p

Gi1/0/5 Root FWD 4 128.5 P2p

VLAN0105

Spanning tree enabled protocol rstp

Root ID Priority 32873

Address

Cost 4

Port 5(GigabitEthernet1/0/5)

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

Bridge ID Priority 32873 (priority 32768 sys-id-ext 105)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/6 Altn BLK 4 128.6 P2p

Gi1/0/3 Altn BLK 100 128.3 P2p

Gi1/0/4 Desg FWD 100 128.4 P2p

Gi1/0/5 Root FWD 4 128.5 P2p

VLAN0215

Spanning tree enabled protocol rstp

Root ID Priority 32983

Address

Cost 4

Port 5(GigabitEthernet1/0/5)

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

Bridge ID Priority 32983 (priority 32768 sys-id-ext 215)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/6 Altn BLK 4 128.6 P2p

Gi1/0/3 Altn BLK 100 128.3 P2p

Gi1/0/4 Desg FWD 100 128.4 P2p

Gi1/0/5 Root FWD 4 128.5 P2p

VLAN0220

Spanning tree enabled protocol rstp

Root ID Priority 32988

Address

Cost 4

Port 5(GigabitEthernet1/0/5)

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

Bridge ID Priority 32988 (priority 32768 sys-id-ext 220)

Address

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

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

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

Gi1/0/6 Altn BLK 4 128.6 P2p

Gi1/0/3 Altn BLK 100 128.3 P2p

Gi1/0/4 Altn BLK 100 128.4 P2p

Gi1/0/5 Root FWD 4 128.5 P2p

MHM Cisco World · ‎12-08-2022

SludgeBldg3850#sh spanning-tree

VLAN0001

Spanning tree enabled protocol rstp

Root ID Priority 8193

Address 0002.17BE.A6E2

Cost 4

Port 1(GigabitEthernet1/0/1)

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

Bridge ID Priority 12289 (priority 12288 sys-id-ext 1)

Address 000A.F316.D050

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

Aging Time 20

why you always change something from previous post? I answer according to your previous post,
first show spanning show that SludgeBLDG have prioirty 32000 then now you share different value 12289 !!!!

I dont know what you are trying here.

anyway make SludgeBLDG have high priority value.

and thanks and good luck.

Outdoor Adventurer · ‎12-08-2022

I appreciate your help. I am not only relying on your expertise but am still trying to figure it out on my own. Perhaps I should have made a copy and worked from there. Thank You.

Martin L · ‎12-08-2022

is this Packet tracer lab ? You can attach your PT file here (must be in a zip format).

PT is just a sim to simulate real IOS; it is not real IOS, not all features are included and those that are may or may not behave as real IOS or device (Cisco and other)

"Packet Tracer offers an effective, interactive environment for learning networking concepts and protocols.
Most importantly, Packet Tracer helps students and instructors create their own virtual “network worlds” for exploration,
experimentation, and explanation of networking concepts and technologies."
*

Regards, ML
**Please Rate All Helpful Responses **

Outdoor Adventurer · ‎12-08-2022

Martin,

Yes - I am using the latest version of Packet Tracer. I have attached the PT file for you with a brief explanation (in addition to this long thread) in the PT file. I believe I am over-complicating it and have successfully configured it. Thank you in advance for taking a look.

Martin L · ‎12-09-2022

the file attached works fine; Close your PT files; reopen one u shared here. DigestBldg3850 link to Sludge are ALT Blocking because Sludge Lower MAC wins with Bridge priority equal (000A.xover 0030.x)

I only see one link on non-existing vlan 200 set up with cost 100; perhaps typo

spanning-tree vlan 200 cost 100

see post STP Designated Port Election in CLN forum, https://learningnetwork.cisco.com/s/question/0D53i00000Kt6RkCAJ/stp-designated-port-election

The selection rules for designated port are as follows:

1. Lowest root path cost (of the switch claiming to be designated bridge for the segment)

2. Lowest BID (of the switch claiming to be designated bridge for the segment)

3. Lowest Port ID.

Also, note that sender is the preferred (Lowest sender BID and Sender Port ID)

Regards, ML
**Please Rate All Helpful Responses **

Outdoor Adventurer · ‎12-10-2022

Martin - Thank you for taking a look at the attached file.

Yes - I verified and the spanning-tree vlan 200 cost 100 command on Gig1/0/4 was a typo that I had missed. Thank you for bringing it to my attention.

When I actually head out to field deploy this configuration, if the link is already blocking due to spanning-trees selection criteria then I am acovered. If not, I will simply set the cost on the DigestBLDG links to SludgeBDLG to 200 to block.

I also configured RSPAN back to the AdminBLDG switch. Assuming that I configured correctly as well?

Again - I appreciate your help.

Martin L · ‎12-10-2022

not sure if PT supports RSPAN commands and configs. check under PT Help . PT is just a sim, not real IOS !

Regards, ML
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