Weird Scenario with switching

gbdavidxgbdavidx Posts: 840Member
I have a weird scenario, trying to practice switching. I have three switches all connected in a triangle like shaped named switch 1, switch 2 and switch 3. When I break the connection between my switch 1, my switch 3 my connection between switch 3 and switch 2 will work, however when all are interconnected, my connection to switch 3 from switch 2 fails

I have attached the diagram of my switched network, what could be the cause of this, all interfaces are up when i do a shw ip interface brief, when I do a tracert from switch2 to switch 3 it goes the long way....

i have no port-security turned on right now

Comments

  • JeanMJeanM Posts: 1,117Member
    2015 goals - ccna voice / vmware vcp.
  • EdTheLadEdTheLad Posts: 2,112Member ■■■■□□□□□□
    You need to do some reading on the spanning-tree protocol.
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
  • gbdavidxgbdavidx Posts: 840Member
    JeanM wrote: »
    According to show IP iny brief all ports are up. The diagram is just showing the amber light
  • aftereffectoraftereffector Posts: 525Member
    Sounds like you made yourself a spanning-tree lab.
    CCIE Security - this one might take a while...
  • gbdavidxgbdavidx Posts: 840Member
    I understand its a STP issue but how do i fix it, i thought this was enabled by default on all switches or do i have to turn it on?
  • networker050184networker050184 Posts: 11,962Mod Mod
    What exactly are you trying to fix? This isn't an issue, it's the way STP works.
    An expert is a man who has made all the mistakes which can be made.
  • Dieg0MDieg0M Posts: 861Member
    If you want to make the light go green just "spanning-tree portfast". Enjoy the meltdown :)
    Follow my CCDE journey at www.routingnull0.com
  • OfWolfAndManOfWolfAndMan Posts: 923Member ■■□□□□□□□□
    Do you know what the purpose of STP is? Ever heard of a broadcast storm?
    :study:Reading: Lab Books, Ansible Documentation, Python Cookbook 2018 Goals: More Ansible/Python work for Automation, IPSpace Automation Course [X], Build Jenkins Framework for Network Automation []
  • gbdavidxgbdavidx Posts: 840Member
    yes and yes, read about it last night, to prevent loops, so this is by design? i'm just trying to grasp the idea and make sure its not something i did wrong
  • xnxxnx Do they matter? UKPosts: 464Member ■■■□□□□□□□
    No, it's just how STP works, you'll cover it in ICND2
    Getting There ...

    Lab Equipment: Using Cisco CSRs and 4 Switches currently
  • networker050184networker050184 Posts: 11,962Mod Mod
    STP prevents loops by ensuring there is no path for a loop to occur. To do this it creates a single path out from the root. Links that are not on this path do not forward traffic. That is what you are seeing here.
    An expert is a man who has made all the mistakes which can be made.
  • gbdavidxgbdavidx Posts: 840Member
  • Jon_CiscoJon_Cisco Posts: 1,772Member ■■■■■■■■□□
    If it allowed both connections to be established then the packets would send out both interfaces.
    When a loop like this occurs packets will be duplicated continually.

    It is worth disabling this and seeing it happen. Just make sure it's a simulation or a lab setup.
  • arrogantbastardarrogantbastard Posts: 61Member ■■□□□□□□□□
    Jon_Cisco wrote: »
    If it allowed both connections to be established then the packets would send out both interfaces.
    When a loop like this occurs packets will be duplicated continually.

    It is worth disabling this and seeing it happen. Just make sure it's a simulation or a lab setup.
    It's the frames that are duplicated and cause mac instability/broadcast storms, not packets (not trying to be rude, just clarifying that)
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