Questions tagged [spanning-tree]

For questions about Spanning Tree Protocol (STP), a common protocol to prevent bridge loops at OSI layer-2.

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Is it possible to configure two loops with the same VLAN in STP? [closed]

I need to make the topology described in the image with STP. Two loops with same VLAN on core switch. It's possible?
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27 views

How does a switch decide what mac to use for Root election in STP?

I know that for the STP a root switch or bridge is to be elected based on the BID that consists of a priority value and the MAC address of a switch if the priority is the same then the MAC is the ...
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19 views

STP Portfast Networks

I have switched network and on all access ports I've configured spanning-tree portfast edge When I enable spanning-tree portfast networks on trunk ports 1/0/51-52 every access port is blocked. Do I ...
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127 views

Network topology with big spanning tree diameter

I have a quite big network with spanning tree diameter 26 (if I count it correctly). It is build on Cisco swithes (mainly Catalyst 2960 and Catalyst 1000, two SG350), running rapid-pvst. It is now ...
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42 views

Mac Instability in STP after topology change!

So I'm learning about STP and I recently been taught that when the topology is changed due to direct or indirect Link failure a Mac Instability could occur, So I was wondering, If the blocked port is ...
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34 views

Non [R]STP switches in LAN ring topology

I am revamping a simple network, which is based on cascaded, standard, unmanaged PoE switches. I am also adding a redundant loop closing wire, from the last switch to the first one, which at the ...
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75 views

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

I recently learnt a rule in STP: only Designated ports forward BPDUs. However, I'm not sure about this in RSTP since ALL switches generate their own BPDUs every few seconds. So, in a certain LAN ...
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96 views

RSTP sending BPDUs out of the network switch?

I need some information about RSTP If the port state is blocking, discarding alternate . Should BPDU be sent to external ports? I cant see any BPDU in wireshark if the port states Alternate,Discarding ...
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35 views

STP configurations

In my design, there will be a few be a few rings of edge switches that are connected to my distribution switch. (alcatel 6860-U28) The distribution switch will then be connected to my core router ( ...
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50 views

Aggregation links and RSTP

If aggregation links are used for redundancy to ensure the devices stay active if a link fails, does RSTP need to be configured due to there being 2 links?
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39 views

How loops appeared when skipped listening and learning state?

In STP convergence process, I just know that after a link failed a blocking port become listening state for 15 seconds then learning state for 15 seconds. I've read a CCNA 200-301 Guide explained me ...
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135 views

Can we use both RSTP and MSTP spanning tree protocols in same network

I have network connecting with 500 users and 50 servers connecting different layer3 switches and layer2 switch. Can i run rstp in few switches and mstp on remaining switches.
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252 views

Recommended switches and routers configurations for a building of 5 floors?

Just recently I had an interview for a network Engineer position. The interviewer asked me the following: You have a building of 5 floors, where each floor has around 30 employees. What is your way of ...
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171 views

Why some situations, PC can connected to trunk port and work fine?

I want to know about tagged and untagged vlan mechanism then I try to configure like this When I connected PC3 to trunk port on Packet Tracer, It doesn't work and a switch dropped PC3's frame if I ...
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256 views

Can link aggregation be substitute for stp protocol?

Can link aggregation be a substitute for STP protocol? I mean can I use 2 links with Link Aggregation to connect two switches for higher availability as an alternative to STP protocol?
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159 views

Using MSTP with RSTP

I have two layer-3 switches connected with two redundant links that I'm trying to run PTP OSPF sessions across, a la: (OSPF) VLAN 1002 - - - - - - - - - - - - / ...
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151 views

How would a bridge loop occur?

As I understand it, STP is used to prevent bridge (/switch) loops, which will typically occur in the case of redundant links on a switch. But how can a loop occur and cause a broadcast storm? If a ...
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189 views

RSTP - minimum hello time?

1) What's the minimum possible "hello time" for Rapid Spanning Tree (RSTP)? Is it possible to reduce the hello time to e.g. 0.1 seconds? 2) Is the minimum dictated by the RSTP standard, or would it ...
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315 views

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

I have a network architecture where each of my N switches is connected to two others, making it a perfect loop. For example see the diagram below: I know that in order to avoid broadcast storms, I ...
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1answer
72 views

RSTP Sync received every 2 minutes after a TC

While digging into logs (debug spanning-tree event has been enabled) in order to troubleshoot communication losses after topology changes. I was able to notice once I triggered a TC, one specific ...
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48 views

Why doesn't STP apply only to broadcast/unknown unicast frames?

All known unicast/multicast frames shouldn't cause loops since they have a known destination. So they can use all the available bandwidth. What am I missing?
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89 views

What is the impact of VTP pruning against RSTP topology?

While working on a network using VTP (without pruning yet), I noticed the STP topology (for VLAN 10 let say as an example) was including all switches even the ones not having any interface in the VLAN ...
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38 views

End to End propagation delay computation for STP

While reading a bunch of details about STP timers on this Cisco website https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/19120-122.html#f1 I could not understand how ...
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103 views

Why does HPE disable STP by default? [closed]

It this certainly true that switches needs STP to avoid loops or broadcasts storms, but recently I saw the configuration of my Hewlett Packard switch and I noticed that it has STP feature disabled by ...
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74 views

Is there a problem with “max age” definition in STP?

In "CCNP and CCIE Enterprise Core ENCOR 350-401 Official Cert Guide" we have this definition of max age: Max age: This is the maximum length of time that passes before a bridge port saves its BPDU ...
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47 views

Endianness of data fields inside BPDU

I'm working on a frame/packet decoder and am seeing inconsistent data regarding the endianness of the MaxAge/Hello/ForwardDelay fields inside a spanning-tree BPDU. Below is a picture of a wireshark ...
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91 views

I have L2 network in Delhi, can it communicate without router to L2 network in Florida, using only STP protocol,

using only STP protocol, no NVE etc should be used, is it feasible
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170 views

Why Do We Use STP (Spanning Tree Protocol) or RSTP (Rapid Spanning Tree Protocol) When Packets are Not Routed Optimally?

I am new to networking so this probably a naive question. I've been reading up on the spanning tree protocol and understand why it's necessary in a network (it prevents loops) and I understand that ...
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128 views

STP Convergence: How does a port initially in blocking state know it needs to change to a designated port?

I am attempting to gain a better understanding of how STP converges when certain state changes occur that affect the STP topology. In this scenario (see below) Switch A (SwA) is the root switch with ...
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1answer
228 views

Why do Designated Ports in STP still send BPDUs if the otherside of the link is blocking?

Is there a particular reason for a Designated Port to continue sending out BPDUs after convergence has occurred on a link where the other side is in a STP blocking state? I get the idea of a ...
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193 views

STP Shut Down Port for Camera on HP Procurve

I have a VLAN dedicated for camera devices. We have learned that some camera ports keep going into the down state, and the logging indicates it is caused by STP: sw404(config)# show logging -r 7 ...
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102 views

STP Priority field and 4 bits in multiples of 4096

For the STP Priority Field, how do you get "multiples of 4096" out of 4 bits?
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323 views

Nexus 6001 How to find source of STM_LEARNING_OVERLOAD

Several time ago I've foud that NX-OS sends STM_LEARNING_OVERLOAD EET: %FWM-4-STM_LEARNING_OVERLOAD: system experiencing unusual number of new address notifications - deferring learn notification for ...
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397 views

802.1Q Tagged BPDU?

Question for didactic purposes where I try to keep it IEEE bound and put Cisco off the discussion unless strictly necessary. I refer to 802.1D-1998 and the question is to understand, after clarifying ...
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80 views

DHCP server access problem

What will stop a PC from receiving an IP address from a DHCP server? Is it STP, VTP, 802.1Q or DTP? What is the most preferable of these?
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66 views

STP Loop with Third Party Switches

STP Loop with Third Party Switches I manage a network mostly comprised of older Avaya ERS 3500 series switches. Recently another department has bought a package that comes with it's own server rack, 2 ...
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154 views

What constitues an STP fail on this setup?

We have a host which has a bonded Ethernet interface. only one is active, at each time, when the other fails, the MAC address moves to the other interface and traffic continues... But at the SP ...
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89 views

Is Spanning Tree Protocol Needed?

If there are two switches connected directly together with two links is spanning tree protocol needed? please see below snippet
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544 views

Cisco nexus STP loopguard

I have cisco nexus switches in vPC and they are connected to HP c7000 blade center switches and all my c7000 blade server has Linux Bridge is running, i believe something went wrong somewhere in Linux ...
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848 views

Should portfast be configured on the physical interfaces or on the logical port-channel, or both?

I'm using a Cisco 3750 switch and have two physical ports configured in a port channel that connects to a router. Should I configure spanning-tree portfast on the physical interfaces or on the port-...
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49 views

What spanning tree IEEE protocol does the Cisco 1252AG Aironet access point support?

Link to data sheet We're running Cisco IOS version 15.2(2)JA1. What version of the IEEE STP is supported on the Cisco Aironet 1252AG access points? We are using the "bridge X protocol ieee" command. ...
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2k views

Why STP has to be disable on Trunk Ports?

I have 5 Switches on a Private Network 10.0.0.0/8 with 8 Vlans. On Access ports is running Rapid STP. On Trunk Ports between Switches should i disable STP or not? I would be very pleased if someone ...
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1answer
667 views

Best Practice for Voice and Data VLAN on single port

We have multiple interfaces currently configured with the below on our Cisco 3750x switch. interface GigabitEthernet1/0/21 switchport access vlan 4 switchport trunk encapsulation dot1q switchport ...
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1answer
271 views

STP packets and QoS

Routing protocol packets are IP packets and therfore they could have different DSCP values to have different priorities (which is implemented by QoS policy) during congestion. How about non-IP packets?...
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587 views

What does “l2protocol peer x” exactly do?

i'm struggeling with some Layer2 Service within one of my customer's MPLS networks. My aim is to provide a L2VPN Service between two ISR4000 Boxes that act as CPE in my MPLS platform. This L2 Service ...
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1answer
1k views

Finding the root cause of Spanning-Tree recalculations (on Cisco Nexus 9000s)

I have a nagging Rapid PVST problem on some Nexus 9000 switches. Rapid-PVST keeps recalculating 3 to 5 times an hour. We have in this topology (summarized): Edge Router ...
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1answer
3k views

spanning-tree port type edge trunk on port-channel vs physical interface

If i configure spanning-tree port type edge trunk on physical interface instead of port-channel does that work? Or i have to do spanning-tree port type edge trunk on port-channel ? Example: ...
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325 views

Strange flooding during installing new switch in network

This is very strange issue i am noticing. In our datacenter we have every switch in rack has cisco vPC configured in short whole datacenter running vPC so there is no loop for spanning-tree anywhere ...
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711 views

RSTP recovery time with Ethernet ring

I am trying to test Rapid Spanning Tree on an Ethernet ring. Most of what I found does not seem to apply to my specific situation, but I am happy to be pointed elsewhere. Specifically, I have one ...
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76 views

Spanning tree protocol

I have a questions regarding STP and i would like to know if STP is only a feature of layer 2 switches? i am on GNS3 and i am trying to enable STP but it tells me that there is no spanning tree ...

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