Questions tagged [spanning-tree]

For questions about Spanning Tree Protocol (STP), originally defined by IEEE 802.1D, to prevent bridge loops at OSI layer-2.

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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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70 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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2answers
56 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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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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1answer
66 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
58 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
51 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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1answer
75 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
111 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
140 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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1answer
38 views

Is STP BPDU Guard automatic timeout a good idea with PortFast? [closed]

(I actually have this issue on an HP network but will use Cisco terminology since I think more people are familiar with that) On edge swtchports intended to face end-user stations we set: PortFast (...
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1answer
165 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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107 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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50 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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1answer
323 views

MSTP and Rapid-PVST+

We have a medium sized network running all Juniper except for one building. This building is shared with another group, and is completely Cisco. We just trunk our VLANs up there. Our Juniper network ...
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3answers
65 views

Using VRRP instead of XSTP

Suppose there is a ring with two routers (L3 switch) and 3 switches. All devices are configured properly.VRRP is configured on both routers and one virtual gateway is introduced to switches and their ...
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1answer
124 views

designated ports and root ports in STP

I am just a bit confused about designated ports in STP, i know how to determine them and the confusion is about the say " designated port is the only port in charge to forward traffic on a segment ". ...
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1answer
150 views

Disable STP and force port state on a Avaya 4950 switch port

I know how to connect a switch on a router Avaya VSP 7200 by disabling STP with the command : no spanning-tree mstp force-port-state enable but how to force port state on a switch Avaya 4950? ...
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33 views

Spanning tree priority values on port-channel

Group Port-channel Protocol Ports ------------------------------------------------------------------------- 1 Po1(U) LACP Gi0/3(P),Gi0/9(P) 4 Po4(U) LACP ...
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2answers
296 views

Spanning tree Priority values

show spanning-tree interface gigabitethernet 0/2 Switch default Instance Role State Cost Prio type -------- ---- ----- ---- ---- ---- MST00 ...
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215 views

Fastest spanning tree in multiple-ring topology

I have a topology in which there is a main ring and some nodes in the main ring have a minor ring. 1- which STP configuration has the fastest convergence time? How would you configure spanning tree ...
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3answers
2k views

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

I have a single ethernet switch. Should I use spanning tree? If there is a redundant link, definitely need to enable STP. In a single switch, how is it possible to have a redundant link? Any other ...
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40 views

Spanning tree - per vlan spanningntree vs rapid spanning tree

Which spanning tree protocol is link state and which one is vector state. We have stp and rapid spanning tree !!
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2answers
295 views

Network Redundancy with LACP Trunking

I would like to set up a redundant link between two switches. I have four ports available to accomplish this. Scenario A: Switch 1 has ports 1+2 trunked together via LACP. They are plugged into ...
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1answer
65 views

Cascading a switch interface to another switch

We have a service provider switch which has an interface that we use to connect to other users over. We have been advised by the SP that we can use this interface how we wish (i.e. feed it into a ...
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393 views

spanning tree RootGuard question on vPC switches

I have following diagram and two distribution switch connected back to back over vPC Related spanning-tree question is it ok to use RootGuard on both distribution switch where access switch is ...
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321 views

How does STP convergence work?

Consider the IEEE 802.1D (first revision) Spanning Tree Protocol. I have read a lot of articles and forum entries about STP convergence. Often I do find contradictions about the convergence mechanics. ...
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199 views

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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288 views

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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3answers
95 views

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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2answers
89 views

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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4answers
1k views

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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2answers
459 views

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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1answer
45 views

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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280 views

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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125 views

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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1answer
706 views

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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1answer
75 views

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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1answer
400 views

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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316 views

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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1answer
398 views

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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2answers
342 views

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 ...
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1answer
340 views

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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1answer
80 views

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 ...
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1answer
71 views

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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1answer
44 views

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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2answers
216 views

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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1answer
115 views

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 ...
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2answers
107 views

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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1answer
137 views

Best way to connect Vlan's / STP / LAG

Am having a problem connecting these concepts together , like when i try thinking of them being ran on the same network. am able to understand each of them separately, But am not able to connect them ...