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 STP used to prevent all traffic looping or just broadcast and multicast?
Let's say we have 3 switches in a logical triangle, each switch connected to the other two. This provides an opportunity for a loop when multicast or broadcast traffic is traveling here. STP is used ...
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Cisco VLAN configurations with WAP - Poor performance
We've recently applied a new modification to our network config.
Separating two SSIDs into a guest \ corporate split config.
All of the VLAN and DHCP scopes are functioning in the way it was designed ...
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What is the difference between message age and maximum age in STP
What is the exact difference between these two values in RSTP and what values it can hold. How is the switch's behavior changes as these values are changed.
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Etherchannel Basics
Assume we have 2 switches connected back to back with 2 links as shown below:
Please see the attached image.
In traditional STP environment,one link will be blocked to avoid Layer2 loops.
So ...
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How does STP calculate the lowest port ID
I was reading about how STP determines which port to block. I was looking at this url https://ciscoiseasy.blogspot.co.uk/2010/10/lesson-20-spanning-tree-protocol.html explicitly this section
The ...
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Cisco: err-disabled due to loop - but there are NO redundant physical paths/ wires/ connections
for the third or fourth time in approx two years we have (painfully) noticed some really strange (at least to us) behaviour in our datacenters:
Uplink-interfaces on access-switches which have only ...
user28154
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VRP: Changing a dynamic bridge priority to a static priority value
On a switch running Huawei VRP: What is the safest way to deconfigure a dynamic priority value on a root bridge and then configure a static priority value?
What's the problem?
I can do this:
[...
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nexus : unable to trace switch port
We have nexus 7000, there are multiple vlans
But I am unable to ping from 10.48.32.0/24 to 10.48.42.0/24
There is user 10.48.32.54 i am unable to trace its switch port,please advise.
Below is ...
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Guidelines for network design of bladecenter
I'm setting up a lab environment consisting of an IBM Bladecenter H (equipped with 4-NICs blade servers and 4 Cisco 3012) and 2 3750 as Aggregate switches.
The blade servers will host VMWare and ...
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STP and LAG Problems
I'm having some trouble with STP on our network. I have created a 3 tier network made up of Dell and Cisco switches. The topology is as follows:
The core consists of two Dell N4032 10Gbps switches in ...
user23673
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when is stp disable
I have a problem with stp(spanning tree protocal),most times we always set port to stp enable.but under the below switch every ports is set stp disable.I want to know the situation about when to set ...
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New to HP Switching. Asking topology questions
I have following design:
When I learn switching i started learning on cisco switches. Now We have 3 hp switches. We have to configure spanning tree between sw1,sw2 and sw3.
All I did was type ...
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Building Spanning-tree link
I have two 3560 switches, and I have 2 uplinks. The goal is to make one link green on both ports on each switch, and the other link amber (standby), so when I pull the active green link out, the other ...
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Does router send STP Packets
I have a doubt.
I have seen in real time simulation in the packet tracer , where the router sends STP packet to switch.
Does router really does that and can you explain since STP is for l2 domain only....
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UDLD disabled interface
We have two cisco c3850 they are uplink with fiber port 10G and i am seeing this error on that trunk (uplink) port
[c3850]-----10G----[c3850]
TenGigabitEthernet1/1/4 is down, line protocol is down (...
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Cisco 2960: RSTP finished when?
I have several Cisco 2960 switches here, all configured for RSTP.
15.0(2)SE6
C2960-LANBASEK9-M
spanning-tree mode rapid-pvst
Topology is as follows:
S1 -- S2 -- S4
\ /
\__S3__/
I ...
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Can anyone explain STP mangling?
There's nothing written about it on the internet. Nothing about if it's currently possible to carry out, or how to counter it. Just this definition copy pasta everywhere:
STP (Spanning-Tree ...
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RSTP and PVST mix in switch fabric
We have a Dell stack switch (running RSTP) connected with a couple of Cisco switches (running PVST), and recently, something happened. I'm not sure where, but in our network, we started getting packet ...
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I'm confused on how spanning tree works
Like take this example:
Also not mentioned in image, lets take:
Segment 1 is between switch 1 and switch 2
Segment 2 is between switch 2 and switch 3
Segment 3 is between switch 3 and switch 1
All ...
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Reason to disable spanning-tree?
I inherited a small setup for a VM complex. It is centrally connected via a Juniper EX Switch Stack (as a virtual chassis). Connected to it via lag/trunks (carrying all the same vlans) are 4 Dell ...
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Strange Global BPDU Filter
The working of BPDU filter configured globally is described as follows:
If that port receives a BPDU it loses its Portfast status and
transitions through the normal Blocking, Learning, Listening, ...
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Multiple spanning tree terminology (CST/IST/CIST) and exact behavior
I have the feeling the more I read about MSTP, the more confused I get. So here we are in order to make things clear once and for all.
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/...
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In RSTP, does port have a state when there is no link on it?
As we know, RSTP merges "disabled", "blocking", "listening" states of STP into one "discarding" state. However, when a port is linked down, let's say no physical link on the port, is there still a ...
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Netgear SFP and trunking between three switches
Can you use SFP stacking with trunking?
We have two Prosafe S3300-28x switches stacked using two SFP cables. These switches also have two 10Gig ports, which we would like to connect to a separate ...
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LACP trunk between BNT layer2/3 switch and Cisco 2960s stack on a bladeCenter H
My objective is to replace a Nortel 5520 stack with a stack of Cisco 2960s.
The old working configuration was using mlt trunk between 5520 and BNT layer 2/3 switch. I will use LACP for the trunk ...
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Spanning Tree -DesignatedPort
What's the interest of Designated Port in STP algorithm ?I didn't get their goal,we have both RootPort and DesignatedPort
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proposal flag and agreement flag in 802.1w RSTP BPDU packet
For my current understanding of RSTP, the proposal flag and agreement flag should not be set to "1" at the same time, and they should also not be set when the network topology is stable, which means ...
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UDLD on Nexus 5548 and Nexus 2232
Do you know if I turn on UDLD the 5K and 2K will speak UDLD to each other and do you feel this is a benefit to detect any link issues between the 5K and the FEX?
Thanks
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Why use one MAC per port design in L2 switch for STP function
While I'm testing the STP function in several different Switches, I found Some Switches use single MAC address for all LAN ports (e.g. Buffalo's BS-G2108M, Netgear's GS716Tv3), while some other ...
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Does the spanning tree protocol come as standard in L3 switches? [closed]
Online there is a lot of content mentioning the spanning tree being a l2 switch feature so I guess it comes as standard/ is a given that it available for all modern l3 switches...
(Could the answer be ...
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Blocking all VLANs between Juniper switches
I have some Juniper switches (Model: ex4550-32f) connected together with trunk ports.
I want to allow VLAN 6 on all below interfaces because it is the main switch and connected to other switches in ...
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Link aggregation: disable spanning tree
It's a simple question, with switch interfaces using etherchannel,is necessary to use bpduguard in these interfaces for that disable Spanning-tree? Because using mode simulation of Packet Tracer, I ...
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How Forward Delay Timer is estimated in Spanning Tree Protocol
From my understanding so far, to estimate forward delay, the following formula should be used.
(end-to-end_bpdu_propagation_delay + message_age_overestimate +
tx_halt_delay + max_frame_lifetime)/2
(...
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Which switch MAC addresses are used for the Bridge ID in STP?
Lets imagine that I have big LAN environment with many switches and many VLANs, for example, VLANs 5,15 and 50. I have PVST+ activated, and all of my switches have same (STP) priority.
I connect a ...
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Trunk link between Cisco switches does not allow internet to the end users
I have a issue in my network. In terms of OSI I am OK in the physical layer. My link is OK because I tested connecting a computer on a fiber link, and I was able to surf the Internet, but when I make ...
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Spanning-Tree Interoperability between ProCurve core & Cisco access layer
I need help regarding the following spanning-tree issue.
I have a network core of 2 HP5412 (procurve) connected together using VRRP over a L2 tagged link.
I have a Cisco 3560 connected to each of the ...
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how to read the STP status (FORWARD/BLOCKING) of each interface/port via SNMP
how can I read the STP port status of each interface (in my software/program)?
There is a MIB called BRIDGE-MIB with OID "dot1dStpPortState=1.3.6.1.2.1.17.2.15.1.3" that returns the FORWARDING OR ...
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PVST with VLANs not matching on switches
How will PVST behave in a situation in which there are two switches connected to each other via access switchports which have different VLANs assigned to them?
Ex:
[Switch 1] Port with "Access Vlan ...
user16942
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Set priority of bridge to 0 but root bridge shows now priority 1 in STP
I have configured a network in Packet Tracer with 5 switches and connected them all together. Then, I configured a priority of 0 and wanted to see how the election of the root bridge takes effect.
...
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Will STP portfast prevent a loop?
I'm trying to understand if two ports on the same switch, are in portfast mode, will a loop be created when the two ports are connected to each other. i.e. if FastEthernet 0/2 and 0/3 are both set to ...
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Behavior about 802.1D with ISL
Reading this quote,
The 802.1Q standard defines one unique Spanning Tree instance to be used by all VLANs in the network.
STP runs on the Native VLAN so that it can communicate with both 802.1Q and ...
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Setting up a new Meraki MS220-48FP Switch to replace a pre-existing DellForce10 Switch
I have a new Cisco Meraki Switch that is replacing a DellForce10 switch that is already in place. I need to configure the Meraki switch to how the Dell switch is setup. The only thing that is ...
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Block MSTP on port Dell N series networking
I am noticing that our Dell N4000 series switch connected to a stack of Cisco devices is constantly attempting to change spanning tree topology. The Cisco switch is our Internet connection and a fiber ...
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Native Vlan Cisco Catalyst and Layer 3 switch
I have run into an interesting issue setting the native VLAN between one of my Cisco Catalyst 2960 and my Layer 3 switch (third party). Here is the setup, the layer three switch is set up to run on ...
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Interoperability CST and PVST
Per-VLAN Spanning Tree+ (PVST+) is an extension of the PVST standard.
Per-VLAN Spanning Tree+ (PVST+) allows interoperability between CST
and PVST in Cisco switches.
What does interoperability ...
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Cisco proprietary protocol - Spanning Tree
I was reading a wiki page about Spanning Tree and the following quote intrigued me: "Both PVST and PVST+ protocols are Cisco proprietary protocols, and few switches from other vendors support them. "
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Current Mode Spanning Tree
What is the current mode Spanning Tree running on Switches, since 802.1W was incorporated into 802.1D-2004? Even being 802.1D or 802.1W still not support VLANs, just Native VLAN has one SPT instance?
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Juniper trunking with two links (not using LAG)
Some reason I'm drawing a blank on this. Let's say I have two EX switches connected together with 2 links to each other (xe-0/1/0 and xe-0/1/1 on both switches).
I can easily setup a trunk on one of ...
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Avoiding switch loop?
Please advise on the following question:
With 2 Cisco 2960G switches connected as in the diagram:
STP is not used.
How could the switches be configured in such a way that all the traffic HOST<-&...
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Why showing IEEE Spanning Tree protocol
I'm preparing for the CCNA and I have a little trouble understanding the outputs for STP.
By default a CISCO switch use PVST (Per VLAN Spanning Tree) but if we use the command show spanning-tree ...
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