Questions tagged [spanning-tree]
For questions about Spanning Tree Protocol (STP), a common protocol to prevent bridge loops at OSI layer-2.
327
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PVST + MST + RSTP network. Possible to make it work?
I have got a network (around 100 switches) which looks like this:
Cisco 2960 - can do PVST, RSTP, MST
MRV mr2228-s2c - can do STA, MSTP
HP 1810 - can do RSTP, STP
Two main Ciscos are linked with ...
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2
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2
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OpenvSwitch Spanning-tree priority for specific Vlan ID
I'm new to the SDN technology,
I have 12 year's experience working with Cisco products,
On Cisco devices, a user can set different STP priority Per VLAN ID
Like :
Switch(config)#spanning-tree VLAN ...
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3
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3
answers
315
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Are the Switches not direct connect to the root-bridge need select root port in the STP circuit?
In the STP circuit like bellow, will the Router2 select a root port? or just the Router1 and Router3 select root port?
in a tutorial it says "all the non-root bridge node will select a root-port, ...
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3
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Does Switch need its own MAC address?
I saw a post say Switch do not need its MAC address, unless it's an administrable Switch for managing.
but I found the spanning-tree protocol need a MAC address of Switch to form STP Root Bridge ID. ...
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5
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4
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Do layer 3 protocols use layer 2 protocols?
I saw the STP on layer 2. The guy that made the tutorial says at the end :
Even though it seems that Layer 2 access layer solutions are slowly
being replaced by blazing fast Layer 3 solutions.
...
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4
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2
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863
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Spanning Tree on the interface that resides at end users
I do not understand why we use portfast and in fact STP on the interface of a switch that is directly connected to end users. Indeed, a user can interfere with the STP election and perform DDoS (that ...
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Does STP create a minimum spanning tree?
From the algorithm described in P&D textbook it looks to be minimum (if all edge weights are 1). Can't find mentions on Wikipedia or a quick google search.
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Spanning-tree MSTR port role
What is the MSTR port role in Spanning-tree ?
It shows up on boundary ports between MST regions and switches running (R)PVST+. Note that it shows up only on the switches running MST.
It seems to ...
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2
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0
answers
256
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How to set portfast default on Dell FTOS Switches?
I'm configuring a Dell S3148 switch running FTOS 9.14.0.1 and I would like to achieve similar functionality of the following Cisco IOS commands:
spanning-tree portfast default
spanning-tree portfast ...
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4
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1
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How to solve a BKN* Port Issue on a cisco catalyst
There is a Cisco ISR 4451 connected with Portchannel to a Catalyst 3850 Stack and there are some VLANs enabled, but only one does not come up for a Portinconsistence. I figure out an Issue on the ...
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As a Spanning Tree Protocol Programmer, how will I know when the root bridge ID election is over?
I am trying to implement IEEE 802.1D. I know how the root bridge id is elected.
Initially, every switch will advertise that they are the root bridge.
Next, it will check whether the bridge ID received ...
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5
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1
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750
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Is Per Vlan Spanning Tree or RPVST an open standard or can it only be implemented by Cisco?
I know there are some standards that are CISCO proprietary but have become open standards. CISCO has also updated the RFC to reflect this. So, is this also true for PVST?
Does Juniper or other ...
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2
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spanning tree loop with bpdufilter on acces port but not on trunk?
┌─────┐ ┌─────┐
| A ┼------┼ B |
└─────┘ └┬───┬┘
└---┘ <-- loop
behold the above drawing. this is a test setup connectin switch A and B, and a test loop
A: cisco ...
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How to resolve a spanning tree issue on a server trunk port?
I am having a very strange spanning-tree issue with Cisco Nexus switches.
My server is connected to the TOR switch with trunk configuration because we have multiple VLANs on the server. When I reboot ...
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2
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How should (per-vlan) STP behave when interconnecting access ports from different vlans on the same switch?
Half of the ports of a switch are in vlan 10, the other half in vlan 20, all untagged. In some specific situations, we need someone in the field to be able to interconnect both vlans without access to ...
- 4,670
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1
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Add links to a port channel group without downtime
There are two trunk links with the same configuration connecting two switches. Currently they are independent links and one is blocked with spanning-tree. I would like to convert these to a single ...
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2
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1
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124
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Spanning tree behaviour - topology change
Regarding a next change we have to do, we are studying spanning tree behaviour.
Does the following statement is true ?
In the case of topology change, if a new BPDU is received:
Currently: Root ...
- 1,085
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126
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Replacing a pair of switches and stp
We need replace to a pair of switches with new ones without interrupting traffic.
In order to do that , for some minutes all 4 switches will be interconnected between them - but we need to avoid stp ...
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2
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Edge detection on designated ports
If a switch doesn't receive a BPDU on a particular port it marks this port as "Edge Port". But any designated port won't receive any BPDU even though it was connected to other switches since their ...
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2
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417
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redundant vpn to remote location with redundant links
I have this situation:
Remote location with 6 devices collecting data and each connected to two VPN routers. Bonding is set up for those computers and data is sent to multicast address. Each VPN ...
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3
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1
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150
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Does a bridge have the three STP timers per port or per bridge (one per bridge)?
I was trying to understand Spanning Tree Protocol and I got confused on some points, so I want to ask for some and double check for others:
Do the three timers(including max_age) exist in the bridge ...
2
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2
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557
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I CAN'T ping PC7
So... I have a set up as below. I ping PC7 from the router. obviously an ARP is sent to determine PC7's MAC address. but it doesnt work. i then decide to set packettracer to simulation mode. i ping ...
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Best way to connect VLANs / STP / LAG
Am having a problem connecting these concepts together, like when I try thinking of them being run on the same network. I'm able to understand each of them separately, but am not able to connect them ...
2
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1
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3k
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What is the EtherType of a BPDU frame sent by a switch which runs Spanning Tree Protocol
I want to know what is the EtherType field of a BPDU frame in various versions and variants of the Spanning Tree Protocol.
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Bridge Assurance with vPC on port type network
I'm running two Nexus 3048 switches as network core and I got an issue when linking another switch (specifically a 2960-X) on the vPC links. Consider the scenario:
+-------+ +-------+
| NX #1 |===|...
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4
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2
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High availability LAN segment with Cisco ISR4451X and 2 x Netgear GS724 - Port-channel vs. BDI vs. BVI?
I have a customer that is getting a new 1Gbps ISP connection and wants his servers connected across two switches for redundancy and protection from:
failure of a router port
failure of a network ...
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2
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1
answer
191
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Trying to configure STP on a small network and have a few questions
I am trying to configure the switches on a network to use STP or RSTP but I'm confused about how to do this. The network consists of 3 switches, all on the default subnet, so a fairly simple setup. ...
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2
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What could cause network to duplicate packets? STP during convergence?
I have understood that real networks have routing changes, leading to out-of-order delivered IP packets. Real networks also have frequent packet loss.
However, what I have not understood is why could ...
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Cabling two access ports on the same switch from different VLANs
Theoretically would I be able to connect two switch ports together with a simple straight/cross cable on the same switch. If the two ports are in different VLANs (eg. 2 and 22) and ports are in ...
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391
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root port election in STP
I have a question about root-port election in STP.
How to determine root-port on switch 3, both fa0/1 and fa0/2 have port-cost back to root switch (switch 0) of 38, receive BPDU from port fa0/3 of ...
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2
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504
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MSTP - different VLAN mapping in different regions
Regarding MSTP, is it possible to have different VLAN mapping for different regions ?
Example:
Region 1:
Instance 1: VLAN 10,20,30
Instance 2: VLAN 40,50,60
Region 2:
Instance 1: VLAN 10,50,60
...
- 1,085
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0
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530
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Adding new switch to Spanning Tree network
Currently studying Spanning Tree, I'm not sure about the behaviour when we add a new switch to an existing STP topology (with cisco pvst+).
Assuming we plug this new bridge called S4 with only one ...
- 1,085
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3
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Doesn't a router stop broadcast?
Well I was at work.
And one of our customers connected a new device to that router. Additionally a switch was already connected to the router.
So there was only the switch connected to the router, ...
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2
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1
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522
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Rapid Spanning Tree Protocol - RSTP Bridge Id isn't RSTP-Priority + Ethernet-MAC
what is the difference between the eth.src Address and the Bridge-System-Id? Sometimes they are the same but mostly not. Attached you will find a screenshot where they are the same.
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Why forward delay in spanning tree
I would have a really basic question... Why the spanning tree have forward delay ? (listening=15s and learning=15s).
Why initially the protocol has been designed like this ?
30 seconds before ...
- 1,085
3
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1
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591
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Spanning tree - port roles and status during root bridge election
Regarding my studies I would like to confirm the three statements below about spanning tree.
When a switch boot or spanning tree is enabled on a switch, the switch ports pass into blocking state 20 ...
- 1,085
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2
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390
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Spanning tree root bridge process validation
A question regarding the spanning-tree protocol. During the root bridge election process, how is the end of the election validated? In other words how does the spanning-tree protocol know when the ...
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When and where to use Spanning-Tree (Portfast)
The tl;dr, in which scenario (switch-to-host, or switch-to-switch) do I use spanning-tree portfast or spanning-tree ...?
We had a catastrophic network outage today. My first question to my boss was "...
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854
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Does a switch generate TCN BPDU when it elects a new root bridge?
what are the scenarios in which a switch generates a TCN BPDU other than when a port goes down or come back up?
switch-1---------------switch-2----------------switch-3
(root bridge) (Non Root)...
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Possible to do a port-channel and STP with three 10Gbps fibre interfaces?
I have two sites that I'm planning to interconnect via three circuits carrying layer 3.
They will be presented via fibre.
The bandwidth of the lines will be: 1Gbps, 1Gbps, and 2Gbps.
Each SFP will ...
- 135
4
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BPDU exchange between RSTP switches
According to the documentation:
BPDU are sent every hello-time, and not simply relayed anymore. With 802.1D, a non-root bridge only generates BPDUs when it receives one on the root port. In fact, a ...
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PVST, PVST+ and RPVST
what are the port states and port roles for the following:
PVST, PVST+ and RPVST?
I did some digging. still, I didn't find an answer to my question.
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Are TCN BPDUs dropped on their way to the root if "message age" gets higher then "max age"?
Normal BPDU gets discarded if the message age field reaches max age.
I'd like to know if it's the same for TCN BPDUs on their way up to the root bridge.
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335
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What happens when a BPDU message age reaches "max age"
I read that every time a BPDU is forwarded by a switch, the message age is incremented by 1.
Also the switch will wait "max age" - "message age" for a new BPDU.
I'd like to know what happens if a ...
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2
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626
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Can't get DHCP to work in Spanning Tree
I'm not entirely sure what I'm doing wrong. I configured the inter-VLAN routing from the main router with the IP addresses I used as default router for the DHCP pools I also set in the main router. I ...
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4
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STP not preventing switching loop
I have a TP Link managed switch that I have enabled STP in, but it's not detecting a loop in the network, and brings the entire lan down. I plug two ends of an Ethernet cable into the switch, which ...
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2
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Feeling lost troubleshooting Trunk and STP configurations on Packet Tracer
I couldn't identify the mistake or what I have missing in the configuration on this network, if anyone of you is welling to check it out this is the link PacketTracerFile
I could not ping from any PC ...
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701
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How is the root bridge determined in spanning tree from BPDU perspective?
I understand how root election works, but can someone explain it in terms of BPDUs? Is a configuration BPDU sent, and does the downstream switch forward the BPDU? What if the downstream switch ...
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Why is blocked edge port still forwarding in RSTP on Juniper EX Switch?
I have one EX Switch connected to my laptop on port ge-0/0/9
set protocols rstp interface ge-0/0/9 edge
set protocols rstp bpdu-block-on-edge
commit
root> show spanning-tree interfaces
it still ...
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167
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Do IEEE 802.1_ protocols use BFS or DFS to find spanning trees?
In computer networking, if we want to prevent loop-topology we use STP(spanning tree protocol) or RSTP(Rapid Spanning Protocol). I have read in Discrete Mathematics that for finding spanning tree two ...
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