Questions tagged [spanning-tree]
For questions about Spanning Tree Protocol (STP), a common protocol to prevent bridge loops at OSI layer-2.
289
questions
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24 views
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?
0
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1answer
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 ...
0
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1answer
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 ...
0
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2answers
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 ...
0
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1answer
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 ...
0
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1answer
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 ...
2
votes
1answer
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 ...
0
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1answer
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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0answers
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 ( ...
0
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2answers
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?
0
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1answer
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 ...
1
vote
2answers
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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2answers
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 ...
0
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1answer
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 ...
1
vote
3answers
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?
0
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3answers
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
- - - - - - - - - - - -
/ ...
1
vote
2answers
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 ...
1
vote
2answers
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 ...
0
votes
2answers
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 ...
1
vote
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 ...
0
votes
1answer
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?
0
votes
1answer
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 ...
0
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1answer
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 ...
0
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1answer
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 ...
2
votes
1answer
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 ...
1
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1answer
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 ...
0
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1answer
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
1
vote
1answer
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 ...
1
vote
1answer
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 ...
1
vote
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 ...
0
votes
1answer
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
...
0
votes
2answers
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?
1
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2answers
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 ...
3
votes
1answer
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 ...
0
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1answer
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?
0
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2answers
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 ...
2
votes
2answers
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 ...
0
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2answers
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
4
votes
0answers
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 ...
5
votes
2answers
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-...
0
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0answers
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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1answer
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 ...
4
votes
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 ...
3
votes
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?...
3
votes
1answer
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 ...
4
votes
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 ...
3
votes
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:
...
4
votes
1answer
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 ...
2
votes
2answers
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 ...
1
vote
2answers
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 ...
