Questions tagged [spanning-tree]
For questions about Spanning Tree Protocol (STP), a common protocol to prevent bridge loops at OSI layer-2.
303
questions
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what is the main function of root bridge and ring master?
When we learn the STP or RSTP,we all learn the election of root bridge, the lowest priority number or MAC address of switch will become the root bridge.So here is my first question:
1.So what can the ...
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1answer
70 views
Why does only the root bridge send RSTP BPDUs after sync?
From a recent packet capture, after the sync process in RSTP, only the root bridge sends RSTP BPDUs every 'hello' interval. Why is it so?
Shouldn't all switches send BPDUs every 'hello' interval since ...
3
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0answers
48 views
Why does RSTP send proposal bit and agreement bit as '1' initially?
From a recent Wireshark capture of a RSTP BPDU on a switch, both proposal and agreement bits were set to '1'.
In my understanding, initially both switches 'propose' themselves as root. The better root ...
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2answers
66 views
The difference between data frame and BPDU in STP
There are two of port states in STP: Disabled and Blocking,and the a website explain their difference
Disabled : This port is shutdown,and it won't send or receive any frame
Blocking : This port won't ...
3
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6answers
134 views
Why does STP choose the lowest bridge ID as the root bridge?
The switch which has the lowest bridge ID can be the root bridge,and the bridge ID is made of priority and MAC address,that is ,
bridge ID = priority + MAC address
So we will choose the switch which ...
2
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1answer
56 views
STP Loop issue on long distance link
I have long distance connectivity between west coast to east cost datacenter via our ISP network as you can see that in following diagram (BSN=Boston, PHX=Phoenix)
Now when ISP-A or ISP-B doing any ...
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2answers
55 views
Ramifications of turning off Spanning Tree for EIGRP network?
Ran into something I've never seen before in a production network I'm new to supporting and wanted to get the communities take on it.
I have an EIGRP network that interconnects about 60 sites across a ...
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1answer
32 views
How can a topology have a switch with 3 segments that are unblocked? (Spanning Tree Protocol)
I am quite confused after doing some research online regarding designated port selection. It looked like to me that each port segment has a designated port and a blocked port? If you look at the ...
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2answers
61 views
RSTP: Max Aging and Device Count
I have a question about the RSTP ethernet swtiches, I have 40 RSTP ethernet switches, they connect with the line topology and root birdge is 23th device on the line.
I am using just 23 device for this ...
0
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1answer
52 views
RSTP Network Switches Port Base MAC Address
How to ethernet managable network switch manage the dynamic table entries although receive "port base MAC address frame" like RSTP,STP protocole ?
I know the dynamic mac table save the ...
0
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1answer
76 views
BPDU Guard With RSTP Devices
I am attempting to secure our switches with BPDU Guard. I have it enabled and I have a pieces of equipment with 2 NIC ports on them of which they can be daisy chained together for data collection. ...
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2answers
82 views
Losing connection when connecting a server to Stratix 5400?
I have a problem that when connecting a server to Stratix 5400 the Stratix loses connection for some seconds which causes a Safety Fault for the line because we have Safety PLC’s any help.
,Software ...
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1answer
336 views
What are the differences between root primary and secondary?
Hello I am new at networking and studying for CCNA.
There is a paragraph like this in the book and I am struggling about understanding well. Maybe it's because english is not my native language.
...
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1answer
73 views
How does STP attack work?
I was reading how STP works and an idea came to my mind.
I thought about an attacker can add a new switch (somehow, i don't know if it can be done remotely) or can manipulate the existing switch's ...
0
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1answer
40 views
Layer 2 path selection
So i know this in stp domain if you want to influence traffic you. Eed to increase the port cost on the undesirable port for the desired vlan or mst instance and it worked for me,but on a non root ...
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1answer
45 views
Why would a unidirectional link failure cause a switching loop?
Based on what I've read so far about UDLD and LoopGuard, it seems that in the case of a unidirectional link failure, a switching loop would form because the blocking port would transition into a ...
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1answer
33 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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2answers
203 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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1answer
56 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 ...
0
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1answer
107 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 ...
2
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1answer
121 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 ...
0
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1answer
207 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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41 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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2answers
87 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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1answer
46 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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2answers
409 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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375 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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1answer
337 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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3answers
797 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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3answers
262 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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2answers
297 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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2answers
320 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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2answers
587 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
90 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 ...
0
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1answer
63 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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1answer
183 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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1answer
52 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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1answer
217 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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1answer
96 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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1answer
61 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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1answer
93 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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1answer
269 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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1answer
153 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
331 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 ...
0
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1answer
369 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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2answers
207 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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2answers
429 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 ...
3
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1answer
638 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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1answer
91 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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2answers
109 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 ...
