LMS4.1: blocking Topology Spanning Tree View

Hello,
After selecting a VLAN in Topology's Spanning Tree View to want see forwarding and blocked ports, all TopologyView Windows hangs for ever (>15min, reproduceable). The cancel button doesnt work, killing from task manager is the only possibility to stop.
The managed network is a Multiple Spanning tree where a HP device is the root bridge for migration reasons.
Steffen

Sorry but that's not a currently offered feature.
It would be nice - the Netsys product that Cisco acquired 18-1/2 years ago (and subsequently abandoned) used to do this quite nicely.

Similar Messages

Prime Infrastructure 2.2 - Network Topology View - Spanning Tree View

Hello Team,
Is it possible on PI 2.2 (latest version) under Maps/Network Topology View to be able to "monitor" the spanning-tree performance?
thanks in advance,
George

Sorry but that's not a currently offered feature.
It would be nice - the Netsys product that Cisco acquired 18-1/2 years ago (and subsequently abandoned) used to do this quite nicely.

View spanning tree configuraton for all the switches in ciscoworks

Hi All,
Is there any way I can see spanning tree configuration for all the switches we have on our networks in Ciscoworks.
Waiting for your kind reply.
Thanks in advance
samir

This can be done from within Campus Manager's Topology Services. Open up the LAN Edge View map, and you should seesome switch clouds on the map. If you drill into one of the clouds, you should see a Spanning Tree option in the right-hand tree. If you expand this, you can visualize the spanning tree for MISTP or even for each VLAN.

Are VTP Advertisements Sent over Spanning Tree Blocked Links?

In a Virtual Terminal Protocol (VTP) domain there are 6506 switches, 4912G units and many 35xx units. There are more than 64 VLANs in use, so there are no redundant links due to the 35xx restriction of 64 spanning trees.
Should this be split into three VTP domains to make sure there are no more than 64 VLANs on any 35xx? In this scenario, some of the switches would be connected to one neighbour in the same domain but to other neighbours in other domains. How can we ensure that the first link is not spanning tree blocked for VTP to work?

First, VTP is passed on VLAN 1 and
can be sent and received through blocked
ports.
Second, spantree topology and VTP are totally independent. So, spantree would still block
or forward normally on a link regardless of whether
the switches on each side are in different VTP
domains.

SGE2010 switches, VLAN's and a blocked port in spanning-tree

Folks,
I have 2 switch groups.
2 SGE2010's with VLAN's defined as 10,20 and 30
Vlan 10 is the management VLAN, and it uplinks to our border router.
Vlan 20 is the workstation VLAN, and all workstations point to the switch as their default GW
Vlan 30 is the ip phone VLAN, and all phones use this as their gateway.
I would like to put a LAG between said switches, we have some servers on the ip phone switch that need to be accessed by the workstation clients, and the single 100mb link through the router is probably not going to be enough.
As I understand it, because the switches have different networks on them, a simple lag will not work. I did create a lag, and assign ip addresses to each side, however in that mode, it doesn't appear I can block vlan 10 from transiting the LAG, and with out that block I will end up with a logical loop, and spanning-tree will block one of the uplinks, or the LAG itself.
I have attached an image with a diagram of our current set up.
Any help/advice would be much appreciated.

Tom,
I remember our conversation a few weeks ago. I did not get a chance to have a go at MSTP, mainly because I have no expierence with it, and looking at the configuration properities, it looks a little daunting.
It has also been a very busy few weeks with the deployment of 200+ phones across several sites, and the system is functioning great with out the LAG trunk, I am just trying to plan for the future.
I made a few postings a few weeks ago, one here and one on the Cisco forums on reddit, and a user there gave me some advice I have been unable to make work (I think it's just wrong), but I would love to go this route if it is in fact possible.
Here is the thread : http://www.reddit.com/r/Cisco/comments/x91tc/vlan_trunks_spanning_tree_and_a_port_blocked/c5kskch
This user implies it's possible to block a VLAN across the LAG which would end the logical loop problems.
It looks like his advice is to make the LAG into a trunk, and then block specific VLAN's from transiting it, but in trunk mode, I can't assign it an IP, so I am sorta wondering how exactly you transport packets across it.
Can you confirm that his advice is in fact incorrect?
If MSTP is my only route, then I suppose it's time to dig into the docs and see If I cant get it up and running.

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.

Multiple Spanning Tree in a Hub and Spoke topology?

My company is planning to implement Multiple Spanning tree into our hub and spoke topology. Is that possible?
Should I divide up the vlans into instances based on assigned switch or assigned department?
Thank You.

hi, everyone,
i have search a internet draft to describe this situation, "Using an LSA Options Bit to Prevent Looping in BGP/MPLS IP VPNs", from "http://www.ietf.org/internet-drafts/draft-ietf-ospf-2547-dnbit-03.txt"
does anyone can tell me how can disable this function and clear the "DN" bit on a cisco router? thanks very much.

Blocked Stack Ports on 2960X-48FPD-L Stack (Unstable Switch Stack!) Spanning Tree?

I am having an issue where 2 2960X-48FPD-L Switches in a redundant flexstack (stack port 1 SW1 to port 2 SW2 and port 2 SW1 to port 1 SW2) ring.
At first running the 15.0(2).EX5 (and earlier EX3, and EX4) version IOS yielded all the ports on the stack master switch refusing to run spanning tree and would only link in amber and not pass any traffic other than CDP information (the slave switch linked in fine).
I upgraded to 15.2(3)E and this solved the problem of the ports not linking in green and participating in spanning tree.
Now, however, about every week or two I lose connectivity to the switch stack and I was able to go to the switch stack locally and found that for some reason the switch stack is blocking and unblocking VLANs on StackPort1 frequently (see below). When I was at the site, I sometimes had connectivity, sometimes not. A stack hard reboot brought everything back up, but this is the second time this has occurred and I would expect the same problem in the next week or so.
Has anyone else run into these issues, and have you found a solution?
I'm guessing that if I either get rid of the redundancy on the switch stack or stack using Ethernet cables between switches the problem will go away, but then what is the point of using stackable switches in a non redundant low speed stack. It seems to me that Spanning tree thinks that I have a spanning tree loop going on with the stack ports which I didn't even think was possible.
What do you think?
Jim
_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:02:59: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking StackPort1 on VLAN0307. Port consistency restored.
Mar 11 09:03:16: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:03:27: %SPANTREE-2-BLOCK_PVID_PEER: Blocking StackPort1 on VLAN0307. Inconsistent peer vlan.
Mar 11 09:03:42: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking StackPort1 on VLAN0307. Port consistency restored.
Mar 11 09:03:46: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:03:47: %SPANTREE-2-BLOCK_PVID_PEER: Blocking StackPort1 on VLAN0307. Inconsistent peer vlan.
Mar 11 09:04:12: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking StackPort1 on VLAN0307. Port consistency restored.
Mar 11 09:04:22: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:04:56: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:05:13: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 207 on StackPort1 VLAN307.
Mar 11 09:05:13: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking StackPort1 on VLAN0307. Inconsistent local vlan.
Mar 11 09:05:30: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:06:00: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:06:04: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking StackPort1 on VLAN0307. Port consistency restored.
Mar 11 09:06:32: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:07:02: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:07:03: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 207 on StackPort1 VLAN307.
Mar 11 09:07:03: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking StackPort1 on VLAN0307. Inconsistent local vlan.
Mar 11 09:07:34: %SPANTREE-2-RECV_BAD_TLV: Received SSTP BPDU with bad TLV on StackPort1 VLAN1.
Mar 11 09:07:45: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking StackPort1 on VLAN0307. Port consistency restored.

Jim,
We have also the same problem with our 2960-X switches (access) connecting to a pair of 4500x (VSS) except our issue is with Portchannel with 2 physical links connecting the 2960xs to the 4500.
If we disconnect one of the physical links from the portchannel everything works fine, but when we connect the same physical link back all users lose connectivity and the physical link starts flapping. Here are some of the messages we see in the logs when both physical links are in the portchannel:
Mar 10 18:00:43 EST: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 1 on Port-channel5 VLAN90.
Mar 10 18:00:43 EST: %SPANTREE-2-BLOCK_PVID_PEER: Blocking Port-channel5 on VLAN0001. Inconsistent peer vlan.
Mar 10 18:00:43 EST: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking Port-channel5 on VLAN0090. Inconsistent local vlan.
Mar 10 18:00:58 EST: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking Port-channel5 on VLAN0001. Port consistency restored.
Mar 10 18:00:58 EST: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking Port-channel5 on VLAN0090. Port consistency restored.
Mar 10 18:01:29 EST: %LINEPROTO-5-UPDOWN: Line protocol on Interface TenGigabitEthernet1/0/1, changed state to down
Mar 10 18:01:37 EST: %LINEPROTO-5-UPDOWN: Line protocol on Interface TenGigabitEthernet1/0/1, changed state to up
Mar 10 18:01:48 EST: %LINEPROTO-5-UPDOWN: Line protocol on Interface TenGigabitEthernet1/0/1, changed state to down
Mar 10 18:01:51 EST: %LINEPROTO-5-UPDOWN: Line protocol on Interface TenGigabitEthernet1/0/1, changed state to up
We have upgraded to 15.0(2a).EX5 and still have the same issue.
We have a ticket open with Cisco and have sent them all the logs and debugs and waiting to hear back from IOS developers.
HTH

Setting up ML cards in 454 so that Spanning Tree one side blocks

Currently we have two ML 1000 cards in our Main ONS 454. We have spanning tree set up on a 3560G switch that brings the IP portion of the SONET to all the other 310's in our network. Now when I do a sh spanning tree on the both ports on the switch that go up to ports 1 on the ML 1000 cards it shows me that both are in forwarding mode. How do I set this up so that one of the is blocking?
Thanks

Hi,
if you remove "encryption mode ciphers aes-ccm tkip" from the radio interface does it help?
it should remain like this:
interface Dot11Radio0
no ip address
no ip route-cache
encryption vlan 1 mode ciphers aes-ccm tkip
ssid WLAN_Corporate
ssid WLAN_HartKitGuest
HTH,
Tiago
If this helps you and/or answers your question please mark the question as "answered" and/or rate it, so other users can easily find it.

Spanning Tree Topology Changes notifications

Hello All,
I've configured RSTP in one of our branch divisions because we decided to add a backup wireless bridge in case one of our fibers gets cut out. Everything is working great , i am getting the desired result, however, i wanted to also syslog the trap msg when a topology change occurs and send it by email. The problem is, i cannot get the root switch to log such an event.
The root switch is a Catalyst 6509, i have tried every level of logging possible, to no avail. I know the trap msg is a notice so i have set my logging to informational, but no change.
I know on c3560's and 3750 i can define to log spanning-tree events, and on my lab setup i do get the trap msgs to my syslog server and email.
What am i missing?! How can i have my Root switch send me that syslog msg?
I do appreciate your help
Thanks in advance!

Hi Sarbjit-2014
Thank you for your response, i dont get any traps msg's at all, doing a sh log on the catalyst will not show me those events.
Below is the output of my sh log ,for obvious reasons i have masked the logging host
Syslog logging: enabled (0 messages dropped, 2 messages rate-limited, 0 flushes,
0 overruns)
Console logging: level debugging, 608 messages logged
Monitor logging: level debugging, 23 messages logged
Buffer logging: level debugging, 608 messages logged
Exception Logging: size (4096 bytes)
Count and timestamp logging messages: disabled
Trap logging: level notifications, 649 message lines logged
Logging to x.x.x.x, 560 message lines logged
I also tried to enter the command spanning-tree logging, but it doesnt seem to be available
Thanks

Spanning Tree and Admin mac address issues srw2048

Ok, I have a somewhat complex problem and hopefully someone may shed some light or have an idea as to whats wrong.
First the scenario:
I have two Cisco Cat 6509's etherchanneled to each other via two fiber cables. One of these is the STP/RSTP root. I have two SRW2048's.. one trunked to each of these 6509 switches. There is also a trunk between the SRW2048's. All this is to create a redundant topology so that if one of the switches fail's the others can still forward packets to each other. Of course the scenario described is in fact a loop that should be handled by STP/RSTP. I have RSTP enabled on all the switches in the scenario (PV RSTP on the cisco switches as they only do Cisco's brand of per vlan spanning tree). There are 3 vlan's configured on each of the srw2048's (2,55,96). There are corresponding vlan's also on the 6509's. I have put the srw2048's management interface into vlan 2.
The problem:
I need to forward packets between the srw2048's primarily and only use the 6509 that is not the root when a failure happens. I have configured the non-root 6509's spanning tree cost on the etherchannel to be higher then the alternate path through the srw's to the root. I can hook everything up and view the spanning tree and see that the srw2048's interface that goes to the non-root 6509 is blocked, and all other interfaces on the other switches are forwarding. I can in fact ping and get to the admin interface on all the switches. Then for some strange reason the admin interface of the srw2048 plugged into the non-root 6509 stops responding. If I disable either the interface its plugged into on the 6509 or the other srw2048 everything starts working again. Sometimes it responds after many failures for no apparent reason. I looked into the mac-address table on the 6509's and they are conflicting, pointing to each other for the mac-address of the broken srw2048. When I clear the mac-table the admin port comes back for about 5 seconds then again goes dark. When reviewing mac-table on the 6509's they are back to pointing to each other. The odd thing (although I haven't confirmed this completely) is that hosts placed into vlan 2 on that same srw2048 seem to work fine. If there was an STP loop or something misconfigured, I would expect it to effect any host in vlan 2 or the other vlan's for that matter on the srw2048 that stops responding. Alas, I am stuck because I need to manage this switch remotely. My only thought is that for some reason even when the STP status is blocked the broken srw2048 is still sending out arp's of its admin interface and bypassing the STP protocol. I have no way to confirm this, but maybe someone has an idea as to what I'm doing wrong, or otherwise offer a solution. For now, I simply removed vlan 2 from the 6509 that the broken srw2048 is plugged into and everything seems fine.
My apologies for such a long post, but this is somewhat complicated. Thanks in advance for any info.
-Geoff
Message Edited by gmyers on 08-19-2008 10:35 PM

To follow up, I had a ticket open with Linksys about this for about 3 months with no resolution. I submitted packet captures, stp outputs, etc and no luck. I gave up and basically had to revert to a manual failover for redundancy. It's no perfect or fast, but it works every time.
Unless linksys issues a firmware upgrade with this as a fix, I doubt we will be able to ever resolve this on our own.

Method-long Spanning-Tree Cost - Nexus and VSS

Hi,
I'have a DC topology with 2x6509 VSS, 2 NX7K, 10xNX5548 and NX2K dual-homed.
My question is about spanning-tree cost in method-long
Between VSS(L2/L3) and NX7Ks(L2) i have 8x10giga links on a crossed VPC, from NX7K point of view, the pathcost to the root (wich is the VSS), is 200.
is this correct ?
what is the cost for 2 and 4x10g links ?
thanks for your replies
Franck

Yes one of the interfaces will be in blocking.

Change of spanning-tree root

Hi,
Would appreciate some advise on the following:
The network has already been configured with spanning-tree root primary as well as secondary.
Reassigning another switch to be the spanning-tree root primary/secondary, will it cause a downtime in the network? If yes, how long?
Thanks,
Christina

I'm assuming PVST (not rapid-PVST nor MST, that should behave better)
It is very hard to give an exact estimate of a downtime. First, it's not going to be a global downtime. You can basically compare the topology with your current root bridge and the one with your new root bridge. The ports that need to block in the new topology will block quickly, in a matter of few seconds. However, the ports that were blocked in the old topology and that need to be forwarding in the new topology will take a little bit more than 30 seconds to become forwarding (15 second listening + 15 second learning phases). The topology change mechanism will age out stale CAM entries in 15 seconds. If you add a little margin for BPDU propagation, I would estimate that you are looking at a connectivity loss of about a minute, in part of your network.
The more blocked ports need to move from the old to the new topology, the most connectivity loss you will experience. Some feature like uplinfast are able to switchover quickly between their uplinks in case of root ID changing and will reduce the downtime dramatically. It's mainly the core bridges that will take time to unblock their port.
Note that you can expect better convergence time when a better root is introduced in the network (you are lowering the numerical value of the secondary root priority so that it takes over the primary) than when the primary root is downgraded into secondary (you increase the numerical value of the primary root so that it becomes worse than the secondary).
Regards,
Francois

Mutiple spanning-tree root bridges

We've started installing some new 3650 switches (replacing 3560's at the access layer) running XE 03.03.05SE. We've run into some problems as a result of "ip device tracking" being on by default, but in the process of debugging I've found that three separate switches all believe they are the spanning-tree root bridge for the same VLANs. The new switches are by default in rapid-pvst mode; the distribution switches are set to rapid-pvst as well. All 3650's are dual-homed.
SW1#sh span vlan 999
VLAN0999
Spanning tree enabled protocol rstp
Root ID    Priority    33767
             Address     78da.6e6f.6d00
             This bridge is the root
             Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority    33767 (priority 32768 sys-id-ext 999)
             Address     78da.6e6f.6d00
             Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 300 sec
Interface           Role Sts Cost      Prio.Nbr Type
Gi1/1/4             Desg FWD 4         128.52   P2p
Gi2/1/4             Desg FWD 4         128.116 P2p
SW2#sh span vlan 999
VLAN0999
Spanning tree enabled protocol rstp
Root ID    Priority    33767
             Address     f40f.1b84.9680
             This bridge is the root
             Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority    33767 (priority 32768 sys-id-ext 999)
             Address     f40f.1b84.9680
             Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 300 sec
Interface           Role Sts Cost      Prio.Nbr Type
Gi1/1/3             Desg FWD 4         128.51   P2p
Gi1/1/4             Desg FWD 4         128.52   P2p
SW3#sh span vlan 999
VLAN0999
Spanning tree enabled protocol rstp
Root ID    Priority    33767
             Address     78da.6e6f.7180
             This bridge is the root
             Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority    33767 (priority 32768 sys-id-ext 999)
             Address     78da.6e6f.7180
             Hello Time   2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 300 sec
Interface           Role Sts Cost      Prio.Nbr Type
Gi1/1/3             Desg FWD 4         128.51   P2p
Gi2/1/4             Desg FWD 4         128.116 P2p
Switch 1 seems to behave as if it is the real root, but this still does not make much sense to me. Does anyone have an explanation? It's been a long time since my switching class, and I very seldom have to deal with spanning-tree issues.

Hi,
Having more than one root switch for a VLAN is definitely a sign of some foul play. A contiguous VLAN can never have more than one root switch. Multiple root switches would occur if, for example, the trunks interconnecting the switches had this VLAN excluded from the list of allowed VLANs, or if they were interconnected by access ports (in a different VLAN) rather than trunks. Another possibility could be an inappropriately constructed MAC ACL or VLAN ACL inadvertently block BPDUs. In any case, this may be a source of serious trouble.
Without further information about your network, it is difficult to suggest anything more specific. Would it be possible to post a diagram explaining your network topology? Also, would it be possible to post the show span root and show span bridge outputs from every switch in your network?
Thank you!
Best regards,
Peter

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

LMS4.1: blocking Topology Spanning Tree View

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