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Two Switches Redundancy

Discussion in 'Networking' started by Mohammad5759, Aug 30, 2019.

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  1. Mohammad5759

    Mohammad5759 Thread Starter

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    Hi Tech Guy Community :
    i have a problem with two switches that are connected together to work as redundant so if one fails the other should continue to work if the other returned one of them should be master and continue to provide connection to the network unfortunately both of them are masters and they work continuously but if i recycle the power on sw1 or sw2 i would totally lose communication both have spanning tree enabled.
    thanks for your assistance ,
    Mohammad.
     
  2. zx10guy

    zx10guy Trusted Advisor Spam Fighter

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    First. What switches are we talking about here? Are the switches connected via stacking cables or through some sort of MLAG/virtual chassis protocol?
     
  3. Mohammad5759

    Mohammad5759 Thread Starter

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    thanks for replying zx10guy ,
    they are DGS-3120-24TC made by D-Link the connection is just a trunk between port 10 on both switches
    and all other connections coming to those switches are from other switches as well this is why they are using spanning tree
    we have 4 sets of switches connected to two redundant then those two redundant switches connect to DGS switches.
     
  4. zx10guy

    zx10guy Trusted Advisor Spam Fighter

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    If you want these switches to function as a single virtual switch, you have to use stacking cables. I looked up the information on these switches. There are two stacking ports on the back of the switch. You have to purchase a specific stacking cable to connect the two switches together over those ports. Per the data sheet, the part number for the 50CM length cable is DEM-CB50. If your switches have CX4 ports for the stacking ports, the part number for that cable is DEM-CB50ICX.

    Without connecting those stacking cables, you're going to run into spanning tree issues as you are now.
     
  5. Mohammad5759

    Mohammad5759 Thread Starter

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    thanks a lot zx10guy , i shall buy those cables and connect them and see how it goes .
    you rule man :).
     
  6. zx10guy

    zx10guy Trusted Advisor Spam Fighter

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    You're welcome. If you feel so inclined, mark this thread as solved.

    If you ever want to get into a discussion on why stacking isn't as preferred any more, let me know. Of course, this also depends on the application and the expertise of the networking staff.
     
  7. Mohammad5759

    Mohammad5759 Thread Starter

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    it is solved now and i have redundancy i've just created a trunk via VLAN trunk setting and set one switch to MSTP and the other to RSTP
    if is switched off sw1 i still have communication if i restarted sw1 i still have communication
    and i've done the same for sw2 and also simulated a power outage where i turned off both of them and then returned the power and i got communication back.
    thanks a lot for your support you have been a great help :).
     
  8. zx10guy

    zx10guy Trusted Advisor Spam Fighter

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    Did you get the stacking cables?

    If you have the switches stacked via the stacking cables, you shouldn't need to use any STP protocols. From what you've written above, you're getting path redundancy via STP.
     
  9. zx10guy

    zx10guy Trusted Advisor Spam Fighter

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    Re-reading your last post, would you also confirm if you did network path testing on multiple VLANs bringing both switches down? I'm having a hard time seeing how network traffic would continue on multiple VLANs over non LAG/redundant links from the switch configured only for RSTP. Both switches in my mind would have to be configured for MSTP. But using MSTP will not allow a LAG to be created from a single, stacked, or virtual switch configured switch to two physically independent switches on the other end of the LAG.
     
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