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9 votes
Accepted

Fastest spanning tree in multiple-ring topology

MSTP and RSTP converge equally fast, MSTP is the current protocol version. Given the topology in your diagram (ugh!) and its tree depth, no STP variant will converge quickly (if at all). xSTP default ...
Zac67's user avatar
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7 votes
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H3C MST BPDU exchange failing

You have a fundamental problem with your configuration, which is that the configuration digests on core and access switches don't match. [Core-sw]dis stp region-configuration Oper Configuration ...
richardb's user avatar
  • 1,608
7 votes

Fastest spanning tree in multiple-ring topology

If you can use Cisco Metro Ethernet switches, you might consider Resilient Ethernet Protocol, which is designed for ring topologies. REP is a protocol used in order to replace the Spanning Tree ...
Ron Trunk's user avatar
  • 67.7k
7 votes

Do I need STP enabled on all switches in a loop?

Generally, a ring is a bad design for Ethernet switches. STP blocks one of the ring links, forming a chain. Traffic between switches on opposite sides need to cross the whole chain, potentially ...
Zac67's user avatar
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5 votes

H3C MST BPDU exchange failing

TL;DR: MST (IEEE 802.1s) exchanges BPDUs only on instance 0. Don't expect BPDUs on the other instances. VLAN-to-instance mapping must be identical on all MST switches (ref: richardb's answer) for ...
Marc 'netztier' Luethi's user avatar
5 votes

BPDU exchange between RSTP switches

Actually a STP/RSTP blocked port requires BPDUs to be received, otherwise it will become unblocked. Here's the output of a show command on one of my production switches, which is a blocked port for ...
Paul Bundschuh's user avatar
5 votes
Accepted

Why does only the root bridge send RSTP BPDUs after sync?

according to comments in the question, the actual topology is two bridges: B1 (root) --- B2. According to the specification (IEEE Std 802.1w-2001, sec 17.7) Configuration Messages are transmitted if ...
Effie's user avatar
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5 votes
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STP convergence process needs detailed explanation, please

It is a continuous process. It is continuous because the root bridge (or any other bridge) can fail. If root fails, new root needs to be selected, and if anyone else fails, affected part of the tree ...
Effie's user avatar
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5 votes
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RSTP / MSTP use cases and best practices

what would be the best practice to achieve separate tree topologies for each of the rings? Forget the rings and reconnect the switches in a tree topology with one or two center switches. This double-...
Zac67's user avatar
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4 votes

RSTP Vs STP Vs MSTP

We're talking about two different versions of spanning-tree, IEEE 802.1D STP standard and IEEE 802.1W RSTP, they cannot work together because 802.1D does not understand RSTP BPDUs, but when a RSTP ...
new_py's user avatar
  • 106
4 votes

RSTP recovery time with Ethernet ring

You need to make sure whether those devices really don't send any xSTP BPDUs on their own (verify by packet capturing) - you cannot trust the documentation at all times possibly pass through xSTP ...
Zac67's user avatar
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4 votes
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Endianness of data fields inside BPDU

The timer fields are not encoded as integer seconds but as a fixed-point number - the first octet means full seconds (more significant), the seconds stands for 1/256 seconds (less significant). 14 00 ...
Zac67's user avatar
  • 85.4k
4 votes

STP convergence process needs detailed explanation, please

The "election" is really a conceptual idea. Each bridge starts out sending its own bridge ID as the root bridge. If it hears a better ID, it starts sending that one. When all bridges are ...
Ron Trunk's user avatar
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3 votes

Brocade/Ruckus per vlan spanning tree vs Cisco

RSTP is an IEEE STP that works on the port level only and is unaware of VLANs. For VLANs to form different spanning trees you require MSTP and an appropriate configuration using multiple instances (...
Zac67's user avatar
  • 85.4k
3 votes

What considerations should I need to have in order to configure a RSTP over a PTP wireless network?

Running spanning tree in such a large, unreliable network is just asking for trouble. You will always have links flapping which will cause spanning tree to continually reconverge. You need to ...
Ron Trunk's user avatar
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3 votes
Accepted

STP interface command shutdown STP globally

For question 1, I think it is normal behavior that you will type the command on interface level and it will be global config mode command for your second question there is no option for disabling ...
Mr.lock's user avatar
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3 votes

In RSTP, where all switches generate their own BPDUs, are they limited to forwarding them only on designated ports? (like in classic STP)

BPDUs are not forwarded, generally. BPDUs are generated and sent on all links, including blocked ones. Topology information contained in the BPDUs can be considered to be forwarded, but the BPDUs ...
Zac67's user avatar
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3 votes
Accepted

BPDU Guard With RSTP Devices

bpdu-guard disables a port when it receives (unwanted) BPDUs. That is its design. You cannot use bpdu-guard with devices that you expect to emit BPDUs in general. The only way to keep bpdu-guard ...
Zac67's user avatar
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3 votes
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Does RSTP also maintain correct mac table entries?

So the real question is: Are mac-address-tables upgraded when there are topology changes in RSTP? Yes. MAC address tables are flushed for the port that receives the topology change notice. BUT: ...
Ron Trunk's user avatar
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3 votes
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How would a switch know that it should forward a frame through a different interface in a STP topology?

A few things you might not be aware of: spanning tree convergence takes place before any traffic is forwarded through the network the MAC/source address table in each switch is learned with the ...
Zac67's user avatar
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3 votes
Accepted

Equivelant of ciscos "spanning-tree portfast disable" in Juniper parlance

Juniper's equivalent of portfast is edge (see the documentation). Ports are non-edge by default, which means you don't have to do anything. If you have something like set protocols rstp interface all ...
Jordan Head's user avatar
  • 7,119
2 votes

How fast can STP, RSTP, and MSTP find a new route?

Realistically, it depends on the size of the current spanning tree and how it is disrupted. In an RSTP or MSTP environment, if an interface goes hard down (eg: it's disconnected or otherwise shut ...
Benjamin Dale's user avatar
2 votes

How do I physically measure the re-convergence delay while RSTP determines the new topology after link loss?

I think you could do this using a SPAN port. Since your switches are redundantly connected, determine which of the two links is the Alternate. Set up a SPAN session using the Alternate port as a ...
John K.'s user avatar
  • 969
2 votes

Why is there a large difference between BPDUs sent and received counters for RSTP root port?

RSTP protocol which is now widely implemented is sending BPDUs only on designated ports. Those 9 are sent during convergence activity in the past.
Viktor Borisov's user avatar
2 votes

RSTP Troubleshooting

15 minute convergence? Ouch! ;) But yes, I agree with your suspicion - multiple 802.1D bridges scattered around the network could easily blow out convergence, as they block all ports other than root ...
Benjamin Dale's user avatar
2 votes

H3C MST BPDU exchange failing

It could be a spanning tree mode related problem. Among RSTP, MSTP and PVST, each mode has some STP compatibility, with a fallback mechanism to STP for ports that receive STP BPDUs. If a MSTP mode ...
Marco De Lellis's user avatar
2 votes
Accepted

Edge detection on designated ports

The switch determines this during the listening phase. If no BPDUs are received during the listening phase, the switch knows it's an edge port.
Ron Trunk's user avatar
  • 67.7k
2 votes
Accepted

Trying to configure STP on a small network and have a few questions

Spanning tree is to prevent layer-2 forwarding loops. It only works if you have multiple bridges (switches are bridges) connected. It works by forwarding frames toward the root bridge, thus preventing ...
Ron Maupin's user avatar
  • 99.9k
2 votes

Does a switch generate TCN BPDU when it elects a new root bridge?

Let me break down as the following: STP is used when you have redundant paths in order to avoid an endless loop which can harm your network. Based on your topology A<->B<->C this is a straight ...
DRP's user avatar
  • 1,491

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