Command Info spanning-tree optimize bpdu transmission

Cannot find any information on CCO, anyone have a link or definition of this command ??

"spanning-tree optimize bpdu transmission" enables the switch to send multiple BPDUs from the interrupt context thereby reducing the CPU usage for the transmission function.
Note that not all platforms support it.
PS: Remember to rate useful posts.

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Spanning Tree PortFast BPDU Guard Enhancement

Will this solve our problems interconnecting 2 ports configured in 2 different vlans?
TIA

Hi Windell,
STP portfast BPDU guard is the feature which is specifically desinged for the ports running stp portfast on them so that a temporary introduction of a switch with lower bridge ID should not disrupt the network topology.At the reception of BPDUs, the BPDU guard operation disables the port that has PortFast configured. The BPDU guard transitions the port into errdisable state.
Please see the link:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a008009482f.shtml
I didnot get your question. Can you eleborate more on this.
regards,
-amit singh

What is the command to check the changes in the spanning-tree topology?

What is the command to check the changes in the spanning-tree topology?

Hi,
Few commands which would help are:
1- Show spanning-tree detail
2-show spanning-tree detail | in ieee|from|occur|is exec >> This will give from were the changes occuring- Ex:
C6K1#show spanning-tree detail | in ieee|from|occur|is exec
VLAN0001 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 9536 last change occurred 00:00:29 ago
from GigabitEthernet4/6
3- show spanning-tree active *& show spanning-tree root >> Will give you the root information.
4- show spanning-tree inconsistentports >> If there are any port which are inconsistent state due to STP features.
STP running MST:
===============
show spanning-tree mst configuration >> Need to check and match the same outputs with the other switches running in the same MST domain/region.
show spanning-tree mst detail
show spanning-tree mst <name of the region>
Debug on STP:
============
debug spanning-tree events/bpdu >> would be good but to be run with more cautious.
HTH
Inayath
*Plz rate if this info is usefull.

Spanning-tree cost

I'm practicing spanning-tree with two 2950 switches (Ver 12.1). I have 3 trunks and 3 vlans. I try to change the cost of the interface (for the 3 vlans) and only 2 vlans change the value after I apply the command. The command is "spanning-tree cost 1" in interface mode. Is there any explanation as why only two of the vlans change the cost? I hope to be clear on the scenario.

Hello Francisco,
as Toshi has explained STP calculstes the cost to the root bridge but it does it by adding the local port cost that receives the BPDU to the path cost in the BPDU.
A switch advertises out its ports not in STP blocking state a BPDU modified in the following manner:
the sender bridge id is that of the local switch
the port id is that of the outgoing port
the total cost to reach the root bridge is:
cost received on root port + cost of root port
notice that only port-id changes from port to port.
This is different from what happens with routing protocols where the cost is added on the outgoing interface.
So as Toshi notes if one device is the root bridge for one vlan the cost (actually 0) doesn't change if you change the cost of one of its ports.
Hope to help
Giuseppe

Spanning tree for VLANS

Hi,
I need an answer to this puzzling scenerio i have been asked to work with.I have two vlans with about 10 switches on each end and there is a link switch that has a connection to both sides of the VLAN. I have been asked to create a singular spanning tree for the entire scenerio. how can i go about this.
please i am awaiting the opinions of anyone knowledgable in this line. thanks.

Hi, I agree you can config MST on your router to reduce the number of spanning tree instances runing on the switch from one per vlan. You will have to map your vlan range to the MST, useful CLI commands are
spanning-tree mode mst
spanning-tree mst configuration
name (name)
revision( revision number)
instance (number) vlan (vlan range)
check your config using
show spanning-tree mst configuration.
Hope thsi will hlep you get started.
DW

Spanning tree in VPC

Hi All,
I have a topology like two vpc peer connected to down catalyst switch 3750 with VPC 51. My left switch is primary in VPC and other is secondary.
So acc. to Theory only primary switch would generate BPDU not secondary switch. But if down catalyst or Secondary switch will be root switch in Spanning tree.
Will primary switch still generate the BPDU's?

Hi Garg,
In VPC environment , In simple term regardless of the Spanning-tree root, VPC primay always generate BPDU and seconday device only rely that bpdu and never generate itself.
For vPC ports only the vPC primary switch runs the STP topology for those vPC ports. In other words, Spanning Tree Protocol for vPCs is controlled by the vPC primary peer device, and only this device generates then sends out Bridge Protocol Data Units (BPDUs) on Spanning Tree Protocol designated ports. This happens irrespectively of where the designated Spanning Tree Protocol root is located. STP on the secondary vPC switch must be enabled but it doesn’t dictate vPC member port state. vPC secondary peer device proxies any received Spanning Tree Protocol BPDU messages from access switches toward the primary vPC peer device . Both vPC member ports on both peer devices always share the same STP port state (FWD state in a steady network).
HTH
Regards,
VS.Suresh.
*Plz rate the usefull posts *

Spanning Tree VLAN Priority Issue

We have two 6500E switches and running spanning tree with rapid-pvst.We have also configured per vlan spanning tree priority with 100,200 so odd vlan have one switch hight priority and even vlans have another switch high priority.
I have created new vlan 10 and tring to add spanning tree priority to the switches i am getting the following error
Core-switch(config)#spanning-tree vlan 10 priority 100
% Bridge Priority must be in increments of 4096.
% Allowed values are:
0 4096 8192 12288 16384 20480 24576 28672
32768 36864 40960 45056 49152 53248 57344 61440
Can some experts help me why i am getting the above message and how can i add the priority to the same as existing vlans

Hi ,
Spanning tree priority can be set in increment of 4096 , any other values will be rejected . if you want to know about priority value of existing vlan execute command show spanning-tree vlan X / show spanning-tree command which will show you switch priority value
Step 2
spanning-tree vlan vlan-idpriority priority
Configure the switch priority of a VLAN.
•For vlan-id, you can specify a single VLAN identified by VLAN ID number, a range of VLANs separated by a hyphen, or a series of VLANs separated by a comma. The range is 1 to 4094.
•For priority, the range is 0 to 61440 in increments of 4096; the default is 32768. The lower the number, the more likely the switch will be chosen as the root switch.
Valid priority values are 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152, 53248, 57344, and 61440. All other values are rejected.
HTH
Sandy

"Peer-switch" command on vPC domain and spanning-tree priority interaction

Hi guy,
We have 2 N7K (N7KA and N7KB) which will be running vPC in hybird and pure vPC environment.
I have a question about the Hybird and pure vPC environment. With the "peer-switch" command enable, should i tune the spanning-tree priority to be the same for all the vlan running on vPC on both N7KA and N7KB? This way, when i enter the "sh spanning-tree vlan X(vPC vlan) detail" command on N7K, it will list both N7K announc itself as "We are the root of the spanning tree".Also the switch running spanning-tree with N7K vPC vlan (Hybird), will see both N7K has the same priority (4096), and it is not desirable for a spanning-tree environment. Therefore, i used the "spanning-tree pseudo-information" on N7KB to tune the spanning-tree priority to "8192" and the switch running spanning-tree with N7K will list N7KB has a priority of 8192(perfect).
However, I notice some strange "show" output on the switch running Port-channel with the N7KA and N7KB. The "Designated bridge" priority is flapping as show on the switch. It is constantly changing between "4096 and 8192" with the same vPC system wide mac address.
Entering the "sh spanning-tree vlan X detail" command repeatly on switch with port-channel toward N7KA and N7KB.
>>sh spanning-tree vlan 10 detail
Port 65 (Port-channel1) of VLAN10 is root forwarding
Port path cost 3, Port priority 128, Port Identifier 128.65.
Designated root has priority 4106, address 0013.05ee.bac8
Designated bridge has priority 4106, address 0013.05ee.bac8
Designated port id is 144.2999, designated path cost 0
Timers: message age 15, forward delay 0, hold 0
Number of transitions to forwarding state: 1
Link type is point-to-point by default
BPDU: sent 5, received 603
one sec later.
>>sh spanning-tree vlan 10 detail
Port 65 (Port-channel1) of VLAN10 is root forwarding Port path cost 3, Port priority 128, Port Identifier 128.65. Designated root has priority 4106, address 0013.05ee.bac8 Designated bridge has priority 8202, address 0013.05ee.bac8 Designated port id is 144.2999, designated path cost 0 Timers: message age 15, forward delay 0, hold 0 Number of transitions to forwarding state: 1 Link type is point-to-point by default BPDU: sent 5, received 603
Configuration:
N7KA
spanning-tree vlan 1-10 priority 4096
vpc domain 200
peer-switch
N7KB
spanning-tree vlan 1-10 priority 4096spanning-tree pseudo-information vlan 1-10 designated priority 8192
vpc domain 200
peer-switch

We have a issue similar to this in our environment. I am trying to upgrade the existing 3750 stack router with 2 Nexus 5596 running VPC between them. For the transition I have planned to create a channel between 3750 stack and 5596's. Once this environment is set, my plan is to migrate all the access switches to N5k.
The issue is when I connect the 3750 port channel to both N5Ks, all the Vlans on 3750 started to flap. If I connect the port channel to only one N5K everything is normal; but when I connect the port channel to both N5K running VPC, vlans are flapping. Any idea what is going wrong here? Am I missing something?

Debug spanning-tree bpdu brought the network down

I'm troubleshooting a pair of Dell Power-Connect switches in a Dell blade chassis connected to a pair of Cisco 4900M switches. I have my 4900M switches set as spanning-tree root and backup root. The Dell switches are connected via LACP trunks to the 4900M's. Dell switch 1 to 4900 #1 and Dell switch 2 to 4900M #2. Both of the Dell switches are reporting as root switches.
I was trying to troubleshoot this yesterday and ran 'debug spanning-tree bpdu' on the primary 4900M. There was a masive amount of BPDU events scrolling by. This debug command actually took the network down. The primary 4900M was non-responsive and the secondary unit had it's CPU go to 100%. The fix was to power cycle the primary 4900M.
Why did this command take my network down?
--Patrick

Typically, the device prioritizes console output ahead of other functions. The debug spanning-tree bpdu generates a lot of output. That is what jumped the CPU to 100% and ultimately caused the device to crash.
You should be very careful with debug commands and log to the internal buffer, instead of the console.
See: http://www.cisco.com/c/en/us/support/docs/dial-access/integrated-services-digital-networks-isdn-channel-associated-signaling-cas/10374-debug.html.

Why does the command "spanning-tree mst simulate pvst disable" exist

That's all really. Why would you turn it off? What is the advantage. If you're not receiving PVST BPDUs, you don't need it, but why turn it off?

When you use the spanning-tree mst simulate pvst disable command, specified MST interfaces that receive a Rapid PVST+ (SSTP) bridge protocol data unit (BPDU) move into the STP blocking state. Those interfaces remain in the inconsistent state until the port stops receiving Rapid PVST+ BPDUs, and then the port resumes the normal STP transition process.
OK, that's what it does, but why? the only effect it has is blocking your ports.

Spanning tree bpdu

Hi all, can anyone tell me 2 things, firstly do only the uplinks on a switch send out bpdu's ? secondly if I disabled spanning tree on the uplink ports would the switch not send any bpdu's out thus the switch not participating in spanning tree to the rest of the network ?

Concept says, by default all switchports are in trunk mode. So if any switch is connectd to a port, it tries to negotiate the trunk & once established, send BPDUs. Thus, all access ports have portfast turned on which denies any BPDUs received on port.
Coming to your point, Yes uplinks will share BPDUs. If ur topology has redundant connections, then you are prone to loops if stp is turned off. However, if ur only concern is to limit the diameter of stp, prefer using "vlan allowed" comand on trunks for stp to limit to specific vlans & thus not flooding entire network.

BPDU-STP Discrpancy - Help Please - spanning-tree portfast bpduguard

Hi,
I get this discrepancy report by the CicoWorks saying that BPDU-STP is disabled on ports (all te ports on my switch). I have seen a document on this and how to enable this Spanning Tree feature but I am not really sure if I need to do this or not? what is the benefit in having or not having this feature enabled? if enabled, then, wont I get into the port disabling and traffic disrruption business? understanding that there is a time out feature available as well.
Thx,
Masood

Hi Masood.
STP BPDUGuard is used only on the ports which are set to STP portfast. As when the portfast is enabled on the switch it trnasitions from blocking --> forwarding as soon as you connect any device on it. If you connect a switch or a bridge, this can cause a STP loop in your network which can bring your entire N/W to halt/down.
STP BPDUguard is specially designed for the edgeports. So as far as you have a centralized control on your network device and no one can connect any device without proper approval (your) ,you can have it disable. But if you understand the potential impact of connecting a switch or a bridge by anyone without proper authority then you might want it enable it on your switch.
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a008009482f.shtml
HTH, Please rate if it does.
regards,
-amit singh

Why did we really need this "spanning-tree extend system-id" command?

Folks,
On the Spanning tree protocol I understood how does this spanning-tree extend system-id command work.
But I have not understood why it is in place? or why do we really need it?
Regards,
Nikhil Kulkarni.

Hi Nikhil,
The STP and RSTP standard specifications mandate that each switch running STP/RSTP must have a unique Bridge ID (BID). Because Cisco runs STP or RSTP in each VLAN separately (called PVST and RPVST or PVRST), in each VLAN, the switch behaves like a standalone (albeit virtual) switch and thus, each STP/RSTP instance is required to have a unique BID to comply with the standard. Simply, having X VLANs means having X separate STP/RSTP instances and X unique BIDs.
The question now is how to make sure the BIDs of STP/RSTP instances run on the same switch in different VLANs are truly unique. Older switches actually had a large reserve of MAC addresses. As new VLANs were created, these switches allocated a new MAC address for each new STP/RSTP instance in a new VLAN (recall that the BID originally consisted of the priority and the MAC address), making the BIDs unique.
However, the consumption of MAC addresses this way was simply too large and ineffective. At the same time, having 65536 different values for priority in the BID was largely useless. So IEEE came with the idea of Extended System ID in which they reused a part of the priority field for a unique instance identifier. In Cisco's implementation, this field is populated with the VLAN number the STP/RSTP instance runs in. This easily and effectively makes the BID unique - even with the same priority for all VLANs on a single switch, and a single switch MAC address, multiple STP/RSTP instances running on this same switch with the same priority have different BIDs thanks to different VLAN numbers embedded into the BID.
Some switch platforms actually allowed you to deactivate the Extended System ID and revert to the older style of assigning unique MAC addresses to individual STP/RSTP instance BIDs. That is why the command spanning-tree extend system-id exists in the first place. However, removing this command is only possible on those switching platforms which are equipped with 1024 MAC addresses for their disposal. Most new switching platforms have only 64 MAC addresses for their internal use, and while the spanning-tree extend system-id command is present in their configuration, you can not remove it. It is simply there to inform you that the Extended System ID is being used but you can not really deactivate it.
Read more here:
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/spantree.html#wp1096536
Best regards,
Peter

Cisco Switches and HP Interoperability with Spanning-Tree (RSTP)

Hello All.
I read a lot of information from this forum about Spaning-Tree interoperability between HP Switches and Cisco Switches.
Rather than having questions I would like to post that I manage to configure successfully HP and Cisco using RSTP (802.1w).
SWPADRAO]display stp root
MSTID Root Bridge ID        ExtPathCost IntPathCost Root Port
  0    32768.cc3e-5f3a-2939 0           0
[SWPADRAO]display stp brief
MSTID      Port                         Role STP State     Protection
  0        GigabitEthernet1/0/47        DESI FORWARDING    NONE
  0        GigabitEthernet1/0/48        DESI FORWARDING    NONE
[SWPADRAO]display stp instance 0
-------[CIST Global Info][Mode RSTP]-------
CIST Bridge         :32768.cc3e-5f3a-2939
Bridge Times        :Hello 2s MaxAge 20s FwDly 15s MaxHop 20
CIST Root/ERPC      :32768.cc3e-5f3a-2939 / 0
CIST RegRoot/IRPC   :32768.cc3e-5f3a-2939 / 0
CIST RootPortId     :0.0
BPDU-Protection     :enabled
Bridge Config-
Digest-Snooping     :disabled
TC or TCN received :17
Time since last TC :0 days 0h:1m:52s
SWNHAM17#show spanning-tree VLAN0001
Spanning tree enabled protocol rstp
Root ID    Priority    32768
            Address     cc3e.5f3a.2939
            Cost        4
            Port        26 (GigabitEthernet0/2)
            Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec  Bridge ID Priority    61441 (priority 61440 sys-id-ext 1)
            Address     001b.54db.7200
            Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec
            Aging Time 300 Interface        Role Sts Cost      Prio.Nbr Type
Gi0/1            Altn BLK 4         128.25   P2p
Gi0/2            Root FWD 4         128.26   P2p
SWNHAM18#show spanning-tree VLAN0001
Spanning tree enabled protocol rstp
Root ID    Priority    32768
            Address     cc3e.5f3a.2939
            Cost        4
            Port        26 (GigabitEthernet0/2)
            Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec  Bridge ID Priority    61441 (priority 61440 sys-id-ext 1)
            Address     001b.0cbc.4300
            Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec
            Aging Time 300 Interface        Role Sts Cost      Prio.Nbr Type
Gi0/1            Desg FWD 4         128.25   P2p
Gi0/2            Root FWD 4         128.26   P2p

Hello, David.
Your command doesn't work because it's made only for tha ports that has command "spanning-tree portfast" in them. Try change spanning tree mode at the HP switch to MSTP if this is possible.

When is it appropriate to use "spanning-tree bpdufilter enable"

What exactly does enabling bpdu filter do? I see some examples where bpdu filtering is enabled on access ports? Is this correct or are there dangers in this approach?

Hi John,
Simple way of saying would that it would disable the STP on that port.
BPDU filter filters the BPDU's coming in both directions. which means it effectively disable the STP on the port.
Detailed explanation:
===============
BPDUfilter on the other hand just filters BPDUs in both directions, which effectively disables STP on the port.Bpdu filter will prevent inbound and outbound bpdu but will remove portfast state on a port if a bpdu is received.Enabling BPDU filtering on an interface is the same as disabling spanning tree on it and can result in spanning-tree loops.
Following are the method to configure BPDU Filter in switches
Interface mode:
spanning-tree bpdufilter enable                        (Results port to not participate in STP, loops may occur).
Global mode:
spanning-tree portfast bpdufilter default             (It enables bpdufiltering on ports that have port-fast configuration, so it sends a few bpdu while enabling port then it filters bdpu unless receives a bpdu, after that itchanges from port-fast mode and disables filtering for port to operate like a normal port cause it has received bpdu).
You always should allow STP to run on a switch to prevent loops. However, in special cases when you need to prevent BPDUs from being sent or processed on one or more switch ports, you can use BPDU filtering to effectively disable STP on those ports.you would use bpdufilter when you want a switch plugged into your network but you don't want it participating in spanning tree.
An example: In an office environment where someone needs another network drop under their desk but you don't have time/budget to run a new line for now. you are been given a small switch but don't want it to break spanning tree.The switch you have lying around for this task is a simple unmanaged switch and will only have one uplink into your network. so you put bpdufilter on your switch port.
Ref:https://supportforums.cisco.com/docs/DOC-11825
HTH
Regards
Inayath
*Plz rate if this info is helpfull and mark as answered if this resolved your query.

Command Info spanning-tree optimize bpdu transmission

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