Spanning-tree modes: PVST vs RAPID-PVST

I am upgrading an old network and as I add switches, I would like them to run rapid-pvst, instead of just pvst which is what the older switches are running.
Last I checked (with a Cisco techie at Networkers 2006), it was OK to have trunked switches with different modes (pvst and rapid-pvst)... but now I'm hearing differently from a few other sources.
Can someone please verify if this is a concern and if so, how should one proceed?
Cheers...

rapid-pvst+ can be migrated into your pvst+ environment.
rapid-pvst+ configured switches revert to pvst+ to provide interoperability.
cisco recommends configuring the rapid-pvst+ and pvst+ for different STP instances. the rapid-pvst+ root switch must be running rapid-pvst+ and the pvst+ root switch must be running pvst+; as well, the pvst+ switches should be at the edge of the network.
(this being said, upgrade your core first and move outward. keep your pvst+ root switch out of the core where rapid-pvst+ will be running)
please see the following link for more info:
http://www.cisco.com/en/US/products/hw/switches/ps5206/products_configuration_guide_chapter09186a00801ce264.html#wp1150840

Similar Messages

Mono spanning-tree and PVST

Refering to these two links
http://www.cisco.com/en/US/tech/tk389/tk390/technologies_tech_note09186a0080094665.shtml
http://www.experts-exchange.com/Hardware/Routers/Q_21349385.html
IEEE 802.1Q defines a single instance of spanning tree running on the native VLAN for all the VLANs in the network which is called Mono Spanning Tree (MST). This lacks the flexibility and load balancing capability of PVST available with ISL. However, PVST+ offers the capability to retain multiple Spanning Tree topologies with 802.1Q trunking.
IEEE 802.1Q defines a single instance of spanning tree running on the native VLAN for all the VLANs in the network which is called Mono Spanning Tree (MST). This lacks the flexibility and load balancing capability of PVST available with ISL. However, PVST+ offers the capability to retain multiple Spanning Tree topologies with 802.1Q trunking.
http://networking.ringofsaturn.com/Certifications/BCMSN.php
Per-VLAN Spanning Tree (PVST) ? A Cisco proprietary method of connecting through 802.1Q VLAN trunks, the switches maintain one instance of the spanning tree for each VLAN allowed on the trunk, versus non-Cisco 802.1Q switches which maintain one instance for ALL VLANs. This is the default STP used on ISL trunks.
http://www.informit.com/content/images/1587051427/samplechapter/1587051427content.pdf
The 802.1Q standard defines one unique Spanning Tree instance to be used by all VLANs in the network. STP runs on the Native VLAN so that it can communicate with both 802.1Q and non-802.1Q compatible switches. This single instance of STP is often referred to as 802.1Q Mono Spanning Tree or Common Spanning Tree (CST). A single spanning tree
lacks flexibility in how the links are used in the network topology. Cisco implements a protocol known as Per-VLAN Spanning Tree Plus (PVST+) that is compatible with 802.1Q CST but allows a separate spanning tree to be constructed for each VLAN. There is only one active path for each spanning tree; however, in a Cisco network, the active path can be
I could not get exactly what these Terminology (PVST, instance, PVST+, MST, etc) trying to achieve ?
Any URL and online resource help me to do some extar reading to clarify these terminology

Hi,
The URLs that you have provided all explains the same technical details in different fashion.
I will summarise them here for better clarity.
There are two separate technologies that needs clarity.
1) Method of Trunking many vlans across a link
2) Spanning tree
Now for point 1, we have the IEEE standard 802.1q, which mentions how multiple vlans can be carried across a link. As per this standard a 4 byte tag will be inserted in the ethernet packet, ( inserted between the Destination mac address field and the ethertype field)
This tag will contain the vlan identifier info and some other details ( available in the urls that you have highlighted)
Cisco has a proprietary technology called ISL which effectively does the same job in a different fashion but can only be used in cisco devices.
Now for point 2, again we have IEEE standards like 802.1d ( common/mono spanning tree), 802.1w/RSTP ( Rapid spanning tree) and 802.1s/MSTP.
In 802.1d, there will be only one spanning tree process/instance running for the whole network, irrespective of how many vlans are involved in the network. Hence the whole network is treated as one common domain by the STP protocol.
So, there can be only one root bridge in the network and other bridges will intelligently block the redundant links, we wont have much control to effectively utilise the redundant links.
IEEE 802.1w/RSTP also works in the same fashion, but the convergence time is very fast in this protocol.
Here also there is only one spanning tree instance involved.
In both the above STP protocols, there is only one instance/process of the protocol running in the network, which is common for all vlans. Hence these protocols consume only very less CPU utilisation.
In 802.1s/ MSTP ( multiple spanning tree), extends the 802.1w Rapid Spanning Tree Protocol (RSTP) to have multiple STP instances. In this protocol, we can group the desired vlans in to one Instance of the protocol.
Say for example, lets assume a typical campus network with multiple access switches, 2 distribution/core switches.
Access switches having dual connectivity to the distribution/core switches.
In this topology if we deploy 802.1d or 802.1w, the redundant links from the access switches to the distribution/core switches will be blocked. Only one uplink from the access switch to the distribution layer will be working at any point.
In this network, only one distribution/core switch will be root bridge for the entire network.
But if we deploy 802.1s for this network, we can design it as follows.
We can split the vlans in to two groups,
Group1 => vlan 1 to 50
Group2 => vlan 51 to 100
We can create two instance of MSTP protocol with the following mappings
Instance 1 => for Group 1, with one distribution/core switch as the root bridge
Instance 2 => for Group 2, with another distribution switch as the root bridge
--Continued

Changing spanning tree modes / potential outages?

Hi All,
Our core / distribution / access layers are all currently configured to use Cisco's PVST+. We are now a fully populated Cisco network with no standards based STP so we can now migrate to Rapid PVST.
By simply changing the spanning tree mode on a an access switch to Rapid PVST will the vlans with spanning tree enabled suffer an outage ? If so will this be time be based on how the rest of the network is configured ? That is, if the rest of the network is still PVST+ and I change a switch to Rapid PVST will the outage deault to around 45 seconds based on PVST+ timers ?
Furthermore, as I understand it, even though this access switch would now be configured for Rapid PVST, the switch defaults back to PVST until the rest of the network (or VLAN) is configured for Rapid PVST.
My second question is this :
Assuming that all the access layer switches have been migrated to Rapid PVST, what would be the effect of then migrating the distributing and potentially core layer devices to Rapid PVST ? Will they also cause an outage on the VLAN on which STP is enabled ? Again, if so, what would the outage be ? Would this be based on PVST timers or Rapid PVST ?
Thanks in advance.
Chris.

Mike
No problem and please do come back if needed.
One thing I should have answered from your questions but didn't directly was the question of the mac address of the root switch.
The mac address that is important in the root switch election is the one contained in the BPDU not the source mac address of the BPDU. The source mac address is simply that of the port that transmitted the BDPU.
If a switch flushes it's mac address table it would remove that mac address but that would make no difference as to whether the switch believed it had lost it's path to root or not.
In terms of switch to switch communication BPDUs are sent with a multicast destination mac address so removing that mac address has no effect on BPDUs being exchanged.
So the fact that you are seeing the switch reporting it has lost it's path to root is not a direct consequence of the mac address being flushed because it doesn't need that to send and receive BPDUs.
However with all the flooding of end to end devices because of the flushing an indirect consequence may be that BPDUs are getting lost.
Apologies for not making that clearer.
Jon

Different spanning tree modes in 1 network

I've noticed that we use MST and PVST in our network, is this a good way to tackle spanning tree ? ( I guess not ) and how am I able to disable MST and use PVST instead.
Also, what impact will it have if I change MST to PVST ?

MST allows you to build multiple spanning trees over trunks. You can group and associate VLANs to spanning tree instances. MST converges faster than PVST.Refer the following URL for more information
http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a008007e71a.html#wp1050594

Challenge: Spanning Tree Control Between 2 links from Switch DELL M6220 to 2 links towards 2 switches CISCO 3750 connected with an stack (behavior like one switch for redundancy)

Hello,
I have an Spanning tree problem when i conect 2 links from Switch DELL M6220 (there are blades to virtual machines too) to 2 links towards 2 switches CISCO 3750 connected with an stack (behavior like one switch for redundancy, with one IP of management)
In dell virtual machine is Spanning tree rapid stp, and in 3750 is Spanning tree mode pvst, cisco says that this is not important, only is longer time to create the tree.
I dont know but do you like this solutions i want to try on sunday?:
Could Spanning tree needs to work to send one native vlan to negociate the bdpus? switchport trunk native vlan 250
Is it better to put spanning-tree guard root in both 3750 in the ports to mitigate DELL to be root in Spanning Tree?
Is it better to put spanning- tree port-priority in the ports of Swicht Dell?
¿could you help me to control the root? ¿Do you think its better another solution? thanks!
CONFIG WITH PROBLEM
======================
3750: (the 2 ports are of 2 switches 3750s conected with a stack cable, in a show run you can see this)
interface GigabitEthernet2/0/28
description VIRTUAL SNMP2
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 4,13,88,250
switchport mode trunk
switchport nonegotiate
logging event trunk-status
shutdown
interface GigabitEthernet1/0/43
description VIRTUAL SNMP1
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 4,13,88,250
switchport mode trunk
switchport nonegotiate
shutdown
DELL M6220: (its only one swith)
interface Gi3/0/19
switchport mode trunk
switchport trunk allowed vlan 4,13,88,250
exit
interface Gi4/0/19
switchport mode trunk
switchport trunk allowed vlan 4,13,88,250
exit

F.Y.I for catylyst heroes - here is the equivalent config for SG-300 - Vlan1 is required on the allowed list on the catylyst side (3xxx/4xxx/6xxx)
In this example:
VLANS - Voice on 188, data on 57, management on 56.
conf t
hostname XXX-VOICE-SWXX
no passwords complexity enable
username xxxx priv 15 password XXXXX
enable password xxxxxx
ip ssh server
ip telnet server
crypto key generate rsa
macro auto disabled
voice vlan state auto-enabled !(otherwise one switch controls your voice vlan….)
vlan 56,57,188
voice vlan id 188
int vlan 56
ip address 10.230.56.12 255.255.255.0
int vlan1
no ip add dhcp
ip default-gateway 10.230.56.1
interface range GE1 - 2
switchport mode trunk
channel-group 1 mode auto
int range fa1 - 24
switchport mode trunk
switchport trunk allowed vlan add 188
switchport trunk native vlan 57
qos advanced
qos advanced ports-trusted
exit
int Po1
switchport trunk allowed vlan add 56,57,188
switchport trunk native vlan 1
do sh interfaces switchport po1
!CATYLYST SIDE
!Must Explicitly allow VLan1, this is not normal for catalysts - or spanning tree will not work ! Even though it’s the native vlan on both sides.
interface Port-channel1
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,56,57,189
switchport mode trunk

Spanning-tree not working: SG500 to Cat3650

Hi All,
Trying to turn up a new site. I have 2 switches: Cat 3650 & SG500-52P. I want to connect up two ethernet cables between these switches in the event one fails, STP will put the blocked one in forwarding. However, when I connect up the 2nd ethernet cable, I get the following:
IPADTBL-N-IPDUPLICATE: Duplicate IP address 192.168.5.232 from MAC a0:ec:f9:ef:6a:18 was detected on VLAN 1, port gi1/1/24
This log message is then followed by the network locking up & crashing until I remove the 2nd cable (i.e. STP Loop). Removing the redundant cable solves the problem. This is because STP is allowing both links to transitioning to forwarding state (confirmed in show spanning-tree & show cdp neighbor).
Why is spanning-tree not correctly blocking one of the lines? Is that type of architecture not supported when there is an SG300/500 in the equation?
Configs below:
Core 3650: (box configs basically)
Switch#show run
Building configuration...
Current configuration : 2686 bytes
! Last configuration change at 10:01:53 UTC Thu Jan 22 2015
! NVRAM config last updated at 09:24:03 UTC Thu Jan 22 2015
version 15.0
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
service compress-config
hostname Switch
boot-start-marker
boot-end-marker
vrf definition Mgmt-vrf
address-family ipv4
exit-address-family
address-family ipv6
exit-address-family
logging console emergencies
enable secret 5 $1$Qi5N$u/5q1HESY/TyQsPFNKVah1
no aaa new-model
clock timezone UTC -6 0
clock summer-time UTC recurring
switch 1 provision ws-c3650-24ts
ip device tracking
diagnostic bootup level minimal
spanning-tree mode pvst
spanning-tree extend system-id
spanning-tree vlan 1 priority 24576
redundancy
mode sso
class-map match-any non-client-nrt-class
match non-client-nrt
policy-map port_child_policy
class non-client-nrt-class
bandwidth remaining ratio 10
interface GigabitEthernet0/0
vrf forwarding Mgmt-vrf
no ip address
negotiation auto
interface GigabitEthernet1/0/1
interface GigabitEthernet1/0/2
interface GigabitEthernet1/0/3
interface GigabitEthernet1/0/4
interface GigabitEthernet1/0/5
interface GigabitEthernet1/0/6
interface GigabitEthernet1/0/7
interface GigabitEthernet1/0/8
interface GigabitEthernet1/0/9
interface GigabitEthernet1/0/10
interface GigabitEthernet1/0/11
interface GigabitEthernet1/0/12
interface GigabitEthernet1/0/13
interface GigabitEthernet1/0/14
interface GigabitEthernet1/0/15
interface GigabitEthernet1/0/16
interface GigabitEthernet1/0/17
interface GigabitEthernet1/0/18
interface GigabitEthernet1/0/19
interface GigabitEthernet1/0/20
interface GigabitEthernet1/0/21
interface GigabitEthernet1/0/22
interface GigabitEthernet1/0/23
interface GigabitEthernet1/0/24
interface GigabitEthernet1/1/1
interface GigabitEthernet1/1/2
interface GigabitEthernet1/1/3
interface GigabitEthernet1/1/4
interface Vlan1
ip address 192.168.5.230 255.255.255.0
ip default-gateway 192.168.5.1
ip http server
ip http secure-server
line con 0
exec-timeout 0 0
stopbits 1
line aux 0
line vty 0 4
password scrubbed
login
line vty 5 15
password scrubbed
login
wsma agent exec
profile httplistener
profile httpslistener
wsma agent config
profile httplistener
profile httpslistener
wsma agent filesys
profile httplistener
profile httpslistener
wsma agent notify
profile httplistener
profile httpslistener
wsma profile listener httplistener
transport http
wsma profile listener httpslistener
transport https
ap group default-group
end
SG500 Switch:
switchff1182#show run
config-file-header
switchff1182
v1.3.0.62 / R750_NIK_1_3_647_260
CLI v1.0
set system mode switch queues-mode 4
file SSD indicator encrypted
ssd-control-start
ssd config
ssd file passphrase control unrestricted
no ssd file integrity control
ssd-control-end cb0a3fdb1f3a1af4e4430033719968c0
voice vlan oui-table add 0001e3 Siemens_AG_phone________
voice vlan oui-table add 00036b Cisco_phone_____________
voice vlan oui-table add 00096e Avaya___________________
voice vlan oui-table add 000fe2 H3C_Aolynk______________
voice vlan oui-table add 0060b9 Philips_and_NEC_AG_phone
voice vlan oui-table add 00d01e Pingtel_phone___________
voice vlan oui-table add 00e075 Polycom/Veritel_phone___
voice vlan oui-table add 00e0bb 3Com_phone______________
hostname switchff1182
no passwords complexity enable
username cisco password encrypted scrubbed privilege 15
ip ssh server
snmp-server server
no ip http server
ip telnet server
interface vlan 1
ip address 192.168.5.231 255.255.255.0
no ip address dhcp
exit
ip default-gateway 192.168.5.1

Hi Peter,
Thanks for replying. Unfortunately (or fortunately if it worked), STP is running and BPDU's are flooding below:
SW500A#show spanning-tree
Spanning tree enabled mode RSTP
Default port cost method: long
Root ID Priority 24577
Address a0:ec:f9:ef:6a:00
Cost 20000
Port gi1/1/43
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address 2c:3e:cf:ff:11:82
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
SW500A#show spanning-tree bpdu
Global: Flooding
I guess I'm doing etherchannels instead of redundant links :-/
This is one of many reasons why I regret these small business models being made; A lot of things that are polished and functional in the enterprise grade (i.e. real switches) just don't seem to work on these units. But unfortunately, as the price is significantly cheaper, companies will continue purchasing these over the better quality units, and engineers like myself will be stuck working with the cut-corners version of a Cisco switch.

Spanning Tree on 2950 (High CPU)

Just swapped out a 2924 with a 2950 (Copying config as closely as the 2950 would allow), and now icmp to Management IP is extremely latent (200m/sec+ from server connected directly to it)....icmp through the 2950 is unaffected.
Spanning tree appears to be the culprit:
36 12275368 3206214 3828 4.99% 4.07% 4.05% 0 Spanning Tree
2950 connects to Cat4k on multiple ports (Both trunks/Non Trunks)
spanning-tree mode is pvst on 2950.
Hoping someone has come across this before :)
Regards,
MB

Further investigation revealed that all the cat4k's vlans where in the 2950's dynamic table (show mac-address-table dynamic) - These vlans where definitely not supposed to be there, so I checked out the interconnecting ports(On Cat4k) to discover that about 5 had turned into trunk ports!(Does CatOS automagically enable trunking on ports in certain circumstances?)
Systematically disabling trunking on these ports stopped all the cat4k's vlans being advertised to the 2950, and also reduced the cpu of spanning tree:
36 15213172 3875075 3925 1.14% 1.37% 1.61% 0 Spanning Tree
icmp had now also dramatically reduced.
Regards,
MB

Spanning-Tree MST

Hi,
we have the following configuration on our switches
spanning-tree mode mst
spanning-tree extend system-id
spanning-tree mst configuration
name test
spanning-tree mst forward-time 4
when we have a failover convergence time was about 8-10 seconds outage is there anything on the above config that suggest's this could be causing the delay? i thought MST was fast convergence times?
Thanks

i will try and you this later on. Not sure it was already in place what are the difference's between them both i thought MST can have multiple vlans per region so better design. Is RSTP not the same as PVST? not done much spanning tree as of yet. so not had chance to look at the differences?
Thanks

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 Reconfiguration - If Root Port is down.

Hello All,
I have some doubt on STP reconfiguration if Root port is down ...Can any one help...?
As per my understanding, if any port is down due to any reason, the corresponding bridge shall sends a TCN to the root bridge through the root port.
Lets say if a root port is down on a bridge, and so, the topology has to be re-established. As the root port itself is down, how does the Bridge convey the TCN to the root bridge ?
Thanks,
RajaSekhar

Hi Raja, if the root port is down, the TCN notification can't make it to the root bridge since the link is down. The affected device will rely on the last known good bpdu. When the affected device has it's designated port down, it will remove the alternate port from discard once it hits the max age table then progress through the listening, learning, forwarding, at this time the new tcn is sent through the spanning tree topology. Once the TCN reached the root bridge, the root bridge will send a configuration bpdu then the whole spanning tree topology will update.
It can take up to 52 seconds to have the topology update in the entirety depending on spanning tree mode and size of topology.
-Tom
Please rate helpful posts

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.

Which spanning tree protocol is preferred PVST or rapid-PVST and why?

I have WS-C2960G-24TC-L and Cisco 3750G switches, I have option to configure PVST spanning tree or rapid-pvst. Please let me know which is better and why? also send me some document explaining both protocols in detail.

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As Alex has noted, normally rapid-PVST should be preferred.
Depending on needs (and device support), MST might be better yet.

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.

Rapid Spanning Tree Question

All,
I have a question about Rapid Spanning Tree reconfiguration. I have to following situation:
As you can see 3 switches with RSTP, and 2 switches without RSTP (or any other spanning tree, just unmanaged).
The 2 switch will form a loop in my network. Switch 1 will block one of the ports and the other port will forward the traffic.
If I break the link "Just Forwarding", my second switch won't be able to cumminucate for around 40 seconds. It will take some time before the backup link will be up again.
Cisco has the Fastforwarding mechanism. Will this help in this situation? I would like to shorten the 40 seconds time.
Thans in advance.

I'd guess the unmanaged devices run legacy spanning tree, and rapid
pvst switches will run rapid according the "heard" protocol. So if it hears
the legacy bpdu, it will run regular spanning tree, hence the 40 second delay.
chris

Rapid Spanning Tree Problem

Hi all,
I am experiencing an RSTP problem. I have two swtitches connected via wireless link, the port is in trunk mode, the native vlan is vlan 1 the problem is that bpdu's are exchanged for other vlan's but not for vlan 1, when i connect a second backup wireless link it causes the loop, it seems that there are no bpdu exchanges between switches for vlan 1, also in trunk ports i see that BPDU's for vlan 1 are sent by both switches but they do not receive any BPDU's from each other. Any explanation about thiss issue ?
Thanks in advance

I would need to know some things to troubleshoot this:
1. Is VLAN 1 the native VLAN of the trunk, on both sides?
2. I presume VLAN 1 is in the allowed VLANs list on both sides of the link?
3. If the native VLAN is not 1, is the native VLAN allowed on the trunk, on both sides?
4. What model of switch is it, and what version of the software?
5. Can you do a show run int for each end of each trunk link?
6. Can you do a show int xxx trunk for each end of each trunk link?
7. Can you do a show spanning-tree vlan 1 on each side of each trunk?
Kevin Dorrell
Luxembourg

Spanning-tree modes: PVST vs RAPID-PVST

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