12 votes
Accepted

Should I disable STP on my access ports?

You really, really do not want to disable STP where you connect switches to other switches. That is the entire purpose of STP. If you disable STP, and there is a problem, it will really be too late ...
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  • 93.5k
11 votes

RSTP vs. STP it really sounds just a big ball of semantics? what's the main difference between them?

RSTP needs backwards compatibility with STP switches. Thus Discarding state merges Disabled, Blocking, Listening into one. Ideally if running a complete RSTP topology then discarding becomes ...
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  • 809
10 votes
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Do layer 3 protocols use layer 2 protocols?

Layer 3 (mostly IP) generally relies on the underlying layer-2 network (mostly Ethernet or Wi-Fi) for delivery. Just like a layer-2 network uses layer-1 links to actually move the bits. The ...
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  • 70.5k
9 votes
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What flags are used in BPDUs in STP?

802.1D STP has configuration BPDUs sent by the root bridge. The designated bridges relay these BPDUs on their designated ports. All BPDUs flow from the root. With 802.1D, a port going up or down will ...
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  • 7,448
9 votes
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STP blocking port selection

you need to understand the next Spanning-Tree Port Roles - Root Port (RP) - It is a port on a non-root switch, which is the shortest (the best) path towards the root bridge. (i.e. port 0/4 0/3 in ...
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  • 3,404
9 votes

Manager states we cannot put retail switches on network due to fear of non-STP config and network storm problems. Is this true?

Great question! This is because a layer-2 switching loop can form on the Consumer-grade switching equipment which could produce Broadcast Radiation and impact devices connected to the broadcast ...
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  • 1,241
9 votes

I have a single ethernet switch. Should I use spanning tree?

To add to Zac67's and JFL's answers: In case you decide to enable spanning-tree on the single switch, don't forget to configure the client's and server's switchports as Edge Ports (Cisco speak; ...
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9 votes
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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 ...
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  • 70.5k
8 votes
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When and where to use Spanning-Tree (Portfast)

Spanning tree only runs between switches, never to standard end hosts. Bear in mind that, under normal circumstances, a port supporting spanning tree will (when it first comes up) run through a ...
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  • 6,028
8 votes
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Does Switch need its own MAC address?

The basic function of a switch is transparent bridging - for this, it doesn't need any MAC address of its own. However, if you need to talk to a switch - ie. a managed switch - then that switch ...
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  • 70.5k
8 votes
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spanning-tree port type edge trunk on port-channel vs physical interface

Strongly suggested: Configure both port-channel and its members identically (except of course for description and the channel-group and vpc bits). As long as an interface is not configured to be ...
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7 votes

VLAN links for IP Cameras

The short answer is, your proposed additional fiber in the diagram will not gain you any real advantage for VLAN 3. All traffic from Packaging or Fiberglass, destined to the server in Shipping on ...
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  • 8,258
7 votes
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How can I determine the STP designated bridge on Cisco IOS?

Found the answer: show spanning-tree interface INT detail This command goes deeper than the regular "show spanning-tree" and displays the designated bridge as well as root bridge.
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  • 943
7 votes

Will STP lose data whilst switching from a failed link?

If i remember, default spanning tree (802.1d) takes about 50 secs to reconverge. That is the duration for which you will be losing frames. A link is detected down by the loss of 10 hello pkts. These ...
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  • 585
7 votes

STP blocking port selection

Some corrections to the above answer. Port-id and port-priority are different. One is configurable. The other is internally set. I'll make an attempt to answer your question below. There has to be ...
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  • 585
7 votes
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Current Mode Spanning Tree

That will depend on the switch vendor, switch model, and software version which the switch is running. When a new standard emerges, it can take some vendors a while to update their code to support ...
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  • 93.5k
7 votes

Multiple spanning tree terminology (CST/IST/CIST) and exact behavior

Now what exactly are the CST, the IST, and the CIST? Can someone draw me a simple MSTP topology with CST in red, IST in yellow, and CIST in green, so as to have a final reference without any ambiguous ...
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7 votes
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I'm confused on how spanning tree works

Yes it did make him go through a more costly path. Maybe you aren't confused on how it works, maybe you're confused on what it's for? Spanning-tree is for stopping network loops. It finds short paths ...
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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 ...
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  • 1,528
7 votes

Is Per Vlan Spanning Tree or RPVST an open standard or can it only be implemented by Cisco?

(R)PVST(+) is a proprietary standard defined by Cisco (or a set thereof). However, there are many other vendors and devices supporting it - you may need to check the specifications of your devices. ...
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  • 70.5k
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 ...
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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 ...
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  • 70.5k
6 votes
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How to prevent possible loop?

Spanning-tree is the protocol designed to detect and prevent loops. bpduguard is intended for access ports -- ports connected to end users/machines (a single node.) A port configured for bpduguard ...
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6 votes
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LACP from Cisco 6509 to Force10 S48-10 - in default VLAN1

Configure your Force10 with portmode hybrid and no spanning-tree pvst err-disable cause invalid-pvst-bpdu on the interface which faces the Cisco 6500... Reference: Force10 - Cisco STP Interoperability ...
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6 votes
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EoMPLS, MSTP, and RPVST

The ME3600s don't support the forwarding of STP or MST frames through EVC. Port based PWE3s will transport STP frames but you will have to chew up a lot of ports. Really you should be engaging your ...
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  • 5,270
6 votes
Accepted

Configure spanning-tree on Cisco router

On a general note: not everything that is present in parser, will actually work on given platform, or even makes sense. In that particular case, you can enable spanning tree if you have either IRB (...
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6 votes

Juniper EX Flooding on STP Topology Change

TCNs are only generated from non-edge ports when they receive a BPDU. Verify that your access ports are configured as edge ports under your spanning-tree config. set protocols rstp interface ge-0/0/...
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  • 538
6 votes

How do I stop %C4K_EBM-4-HOSTFLAPPING message for wireless ports, but leave on for STP issues?

One thing to consider is the rate of flapping. Having worked with a wireless environment with no channel plan or power adjustments and automatic adjustments and channel selection disabled, constantly ...
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