How does STP convergence work?
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Consider the IEEE 802.1D (first revision) Spanning Tree Protocol. I have read a lot of articles and forum entries about STP convergence. Often I do find contradictions about the convergence mechanics. Some people state that convergence follows this schematics:
- Root bridge election
- Root port selection
- Designated ports selection
- Non-designated port selection
Others state that each port cycles through 4 states (Blocking, Listening, Learning, Forwarding). I don't understand how they each connect and how the root bridge election for example takes part in those 4 states. For me, both "models" don't go along with each other, but each part of both of them are neccessary to make STP work in my opinion. The problem, however, is not understanding how each state behaves in terms of packet discarding/MAC learning/etc.. The problem is understanding how it all works together.
Unfortunately, the IEEE standard doesn't help with unterstanding, yet it makes things harder to grasp for me.
Edit: my question was marked as a duplicate to Spanning tree - port roles and status during root bridge election. First of all, the answer doesn't explain the whole convergence process. Furthermore, I don't understand how a bridge decides that it is not connected to another bridge performing STP. How long will it until it decides it is alone and probably the root bridge? When does it stop propagating this?
spanning-tree layer2 redundancy loop
asked 5 hours ago
cmatef8
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up vote
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Consider the IEEE 802.1D (first revision) Spanning Tree Protocol. I have read a lot of articles and forum entries about STP convergence. Often I do find contradictions about the convergence mechanics. Some people state that convergence follows this schematics:
- Root bridge election
- Root port selection
- Designated ports selection
- Non-designated port selection
Others state that each port cycles through 4 states (Blocking, Listening, Learning, Forwarding). I don't understand how they each connect and how the root bridge election for example takes part in those 4 states. For me, both "models" don't go along with each other, but each part of both of them are neccessary to make STP work in my opinion. The problem, however, is not understanding how each state behaves in terms of packet discarding/MAC learning/etc.. The problem is understanding how it all works together.
Unfortunately, the IEEE standard doesn't help with unterstanding, yet it makes things harder to grasp for me.
Edit: my question was marked as a duplicate to Spanning tree - port roles and status during root bridge election. First of all, the answer doesn't explain the whole convergence process. Furthermore, I don't understand how a bridge decides that it is not connected to another bridge performing STP. How long will it until it decides it is alone and probably the root bridge? When does it stop propagating this?
spanning-tree layer2 redundancy loop
asked 5 hours ago
cmatef8
114
New contributor
cmatef8 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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Possible duplicate of Spanning tree - port roles and status during root bridge election
– Zac67
5 hours ago
1
I guess the part you are missing is that STP is always sending BPDUs.
– Ron Maupin♦
4 hours ago
@RonMaupin is STP also sending BPDUs if a port is blocked?
– cmatef8
4 hours ago
2
Yes. It is blocking data frames from being received, but it needs to be able to determine topology changes.
– Ron Maupin♦
4 hours ago
@RonMaupin Does a port even send bpdu if their role is Root Port?
– cmatef8
4 hours ago
|
show 1 more comment
up vote
2
down vote
favorite
up vote
2
down vote
favorite
Consider the IEEE 802.1D (first revision) Spanning Tree Protocol. I have read a lot of articles and forum entries about STP convergence. Often I do find contradictions about the convergence mechanics. Some people state that convergence follows this schematics:
- Root bridge election
- Root port selection
- Designated ports selection
- Non-designated port selection
Others state that each port cycles through 4 states (Blocking, Listening, Learning, Forwarding). I don't understand how they each connect and how the root bridge election for example takes part in those 4 states. For me, both "models" don't go along with each other, but each part of both of them are neccessary to make STP work in my opinion. The problem, however, is not understanding how each state behaves in terms of packet discarding/MAC learning/etc.. The problem is understanding how it all works together.
Unfortunately, the IEEE standard doesn't help with unterstanding, yet it makes things harder to grasp for me.
Edit: my question was marked as a duplicate to Spanning tree - port roles and status during root bridge election. First of all, the answer doesn't explain the whole convergence process. Furthermore, I don't understand how a bridge decides that it is not connected to another bridge performing STP. How long will it until it decides it is alone and probably the root bridge? When does it stop propagating this?
spanning-tree layer2 redundancy loop
asked 5 hours ago
cmatef8
114
New contributor
cmatef8 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Consider the IEEE 802.1D (first revision) Spanning Tree Protocol. I have read a lot of articles and forum entries about STP convergence. Often I do find contradictions about the convergence mechanics. Some people state that convergence follows this schematics:
- Root bridge election
- Root port selection
- Designated ports selection
- Non-designated port selection
Others state that each port cycles through 4 states (Blocking, Listening, Learning, Forwarding). I don't understand how they each connect and how the root bridge election for example takes part in those 4 states. For me, both "models" don't go along with each other, but each part of both of them are neccessary to make STP work in my opinion. The problem, however, is not understanding how each state behaves in terms of packet discarding/MAC learning/etc.. The problem is understanding how it all works together.
Unfortunately, the IEEE standard doesn't help with unterstanding, yet it makes things harder to grasp for me.
Edit: my question was marked as a duplicate to Spanning tree - port roles and status during root bridge election. First of all, the answer doesn't explain the whole convergence process. Furthermore, I don't understand how a bridge decides that it is not connected to another bridge performing STP. How long will it until it decides it is alone and probably the root bridge? When does it stop propagating this?
spanning-tree layer2 redundancy loop
spanning-tree layer2 redundancy loop
asked 5 hours ago
cmatef8
114
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cmatef8 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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asked 5 hours ago
cmatef8
114
New contributor
cmatef8 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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edited 5 hours ago
asked 5 hours ago
cmatef8
114
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asked 5 hours ago
cmatef8
114
asked 5 hours ago
cmatef8
114
114
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cmatef8 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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New contributor
cmatef8 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
cmatef8 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Possible duplicate of Spanning tree - port roles and status during root bridge election
– Zac67
5 hours ago
1
I guess the part you are missing is that STP is always sending BPDUs.
– Ron Maupin♦
4 hours ago
@RonMaupin is STP also sending BPDUs if a port is blocked?
– cmatef8
4 hours ago
2
Yes. It is blocking data frames from being received, but it needs to be able to determine topology changes.
– Ron Maupin♦
4 hours ago
@RonMaupin Does a port even send bpdu if their role is Root Port?
– cmatef8
4 hours ago
|
show 1 more comment
Possible duplicate of Spanning tree - port roles and status during root bridge election
– Zac67
5 hours ago
1
I guess the part you are missing is that STP is always sending BPDUs.
– Ron Maupin♦
4 hours ago
@RonMaupin is STP also sending BPDUs if a port is blocked?
– cmatef8
4 hours ago
2
Yes. It is blocking data frames from being received, but it needs to be able to determine topology changes.
– Ron Maupin♦
4 hours ago
@RonMaupin Does a port even send bpdu if their role is Root Port?
– cmatef8
4 hours ago
Possible duplicate of Spanning tree - port roles and status during root bridge election
– Zac67
5 hours ago
Possible duplicate of Spanning tree - port roles and status during root bridge election
– Zac67
5 hours ago
1
1
I guess the part you are missing is that STP is always sending BPDUs.
– Ron Maupin♦
4 hours ago
I guess the part you are missing is that STP is always sending BPDUs.
– Ron Maupin♦
4 hours ago
@RonMaupin is STP also sending BPDUs if a port is blocked?
– cmatef8
4 hours ago
@RonMaupin is STP also sending BPDUs if a port is blocked?
– cmatef8
4 hours ago
2
2
Yes. It is blocking data frames from being received, but it needs to be able to determine topology changes.
– Ron Maupin♦
4 hours ago
Yes. It is blocking data frames from being received, but it needs to be able to determine topology changes.
– Ron Maupin♦
4 hours ago
@RonMaupin Does a port even send bpdu if their role is Root Port?
– cmatef8
4 hours ago
@RonMaupin Does a port even send bpdu if their role is Root Port?
– cmatef8
4 hours ago
|
show 1 more comment
1 Answer
1
active
oldest
votes
up vote
4
down vote
I don't understand how a bridge decides that it is not connected to
another bridge performing STP.
If it doesn't hear BPDUs, then there's no bridge connected.
How long will it until it decides it is alone and probably the root
bridge?
It starts out assuming it's "alone." That is, the bridge sends BPDUs with its bridge ID as the root until it hears a better one.
When does it stop propagating this?
If by "this" you mean the ID of the root bridge, it's in every BPDU sent.
answered 5 hours ago
Ron Trunk
33.2k22970
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
4
down vote
I don't understand how a bridge decides that it is not connected to
another bridge performing STP.
If it doesn't hear BPDUs, then there's no bridge connected.
How long will it until it decides it is alone and probably the root
bridge?
It starts out assuming it's "alone." That is, the bridge sends BPDUs with its bridge ID as the root until it hears a better one.
When does it stop propagating this?
If by "this" you mean the ID of the root bridge, it's in every BPDU sent.
answered 5 hours ago
Ron Trunk
33.2k22970
add a comment |
up vote
4
down vote
I don't understand how a bridge decides that it is not connected to
another bridge performing STP.
If it doesn't hear BPDUs, then there's no bridge connected.
How long will it until it decides it is alone and probably the root
bridge?
It starts out assuming it's "alone." That is, the bridge sends BPDUs with its bridge ID as the root until it hears a better one.
When does it stop propagating this?
If by "this" you mean the ID of the root bridge, it's in every BPDU sent.
answered 5 hours ago
Ron Trunk
33.2k22970
add a comment |
up vote
4
down vote
up vote
4
down vote
I don't understand how a bridge decides that it is not connected to
another bridge performing STP.
If it doesn't hear BPDUs, then there's no bridge connected.
How long will it until it decides it is alone and probably the root
bridge?
It starts out assuming it's "alone." That is, the bridge sends BPDUs with its bridge ID as the root until it hears a better one.
When does it stop propagating this?
If by "this" you mean the ID of the root bridge, it's in every BPDU sent.
answered 5 hours ago
Ron Trunk
33.2k22970
I don't understand how a bridge decides that it is not connected to
another bridge performing STP.
If it doesn't hear BPDUs, then there's no bridge connected.
How long will it until it decides it is alone and probably the root
bridge?
It starts out assuming it's "alone." That is, the bridge sends BPDUs with its bridge ID as the root until it hears a better one.
When does it stop propagating this?
If by "this" you mean the ID of the root bridge, it's in every BPDU sent.
answered 5 hours ago
Ron Trunk
33.2k22970
answered 5 hours ago
Ron Trunk
33.2k22970
answered 5 hours ago
Ron Trunk
33.2k22970
answered 5 hours ago
Ron Trunk
33.2k22970
33.2k22970
add a comment |
add a comment |
cmatef8 is a new contributor. Be nice, and check out our Code of Conduct.
cmatef8 is a new contributor. Be nice, and check out our Code of Conduct.
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Possible duplicate of Spanning tree - port roles and status during root bridge election
– Zac67
5 hours ago
1
I guess the part you are missing is that STP is always sending BPDUs.
– Ron Maupin♦
4 hours ago
@RonMaupin is STP also sending BPDUs if a port is blocked?
– cmatef8
4 hours ago
2
Yes. It is blocking data frames from being received, but it needs to be able to determine topology changes.
– Ron Maupin♦
4 hours ago
@RonMaupin Does a port even send bpdu if their role is Root Port?
– cmatef8
4 hours ago