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  • Help with understanding why router blocked network

    Hi

    In my topic Network Down I eventually discovered that a wireless router was causing the network to go down. Restarting it would bring the network back up again.

    The router in question served two purposes: It provided wireless connectivity and also acted as a 'desktop switch'. Please note that the router was not used as the gateway to the Internet. It was purely internal.

    It was connected by a 30m cable to a wall socket and had two PC's connected to it.

    I am presently adding detailed TCP/IP documentation to my network documentation which is intended to help someone learn DNS and understand how it works on our network. Whilst writing this I was thinking about DNS resolvers sending queries for IP addresses etc and how the client then connects to that IP address.

    This had me thinking about the router issue and I was wondering how a single device was able to incapacitate the entire network. The router was essentially 'out on a limb' and only provided general wireless connectivity and was physically connected to just two clients and a wall socket.

    Does anyone know why this may have happened, what may have caused it? Searching using such general terms as router and blocked and network does not help as there are gazillions of results for routers used as gateways between networks. As this sat within the network and was not used as a gateway (except for the wireless connections) those results do not seem to apply.

    If anyone has any links to resources that I can read I would appreciate it if you could post them.

    Thanks

    I've attached a diagram I am using as part of the documentation and have edited it to include the problem wireless router so you can see where it is located.
    Attached Files
    A recent poll suggests that 6 out of 7 dwarfs are not happy

  • #2
    Re: Help with understanding why router blocked network

    I had the same problem last week.

    IF I'M UNDERSTANDING CORRECTLY,(may not be LOL)this is more of a comment than help, but i've been using the same method for a few years, with no issues. using wireless routers(3 of them) as access points. not using WAN, turning dhcp off and allow my asa to give out addresses.

    it started when i was setting up and trying to figure out vlans.

    I left a dhcp vlan on asa giving out address diffrent than what i had been using for years, that i had plugged into the switch that everyone was using. Took an hour to figure out that computers plugged into that switch were getting the vlan dhcp.

    i would unplug the wireless, they would get the original ipaddess, then it would switch back to the vlan after 10 minutes.

    i finally realized the computers were getting the vlan dhcp, i disabled the vlan and all is well.


    doubt if this helps, but wanted to share.

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    • #3
      Re: Help with understanding why router blocked network

      Thanks very much for responding. I'm open to any and all suggestions as I don't have a clue why this happened so am happy to read anything that may help.

      The network was fine before and is fine afterwards. No changes were made to the network topography before the wireless device was installed.

      I had some network specialists in to help me fix this before I discovered what was causing the problem. They mentioned that a device can stop transmitting data for a particular port if it encounters bad packets.

      The main reason I am flummoxed is that the router, as you can see from the diagram is 'out on a limb'. Why would that device bring the entire network to a stand-still.

      I'm sure there's a reasonable explanation but my networking knowledge is not up to the task of working it out.

      Thanks again
      A recent poll suggests that 6 out of 7 dwarfs are not happy

      Comment


      • #4
        Re: Help with understanding why router blocked network

        What is the make/model of the switch in the Patch Panel? I am thinking about the first time I came across a Cisco switch which I thought had a bad port. Turns out it was the connection on the end of the port disabling it to save the network from being infected with bad traffic. Can't remember the protocol but it was something like STP. (Need to get a Cisco switch to remember this stuff) (Not a real good description but it is 2.47am local time). I wonder if you wireless router was causing the Uplink port on the Switch to the Gateway Router to trip and kill outside access.

        Must go and find another bale of hay as I am running out of straws to clutch.
        1 1 was a racehorse.
        2 2 was 1 2.
        1 1 1 1 race 1 day,
        2 2 1 1 2

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        • #5
          Re: Help with understanding why router blocked network

          There are two patch panels and two switches in the set that serve the main segment which is the segment that the wireless router is located in.

          The patch panels are a 24 and 12 port model, and the switches comprise two 24 port models: a Zyxel ES1100-24 and an SMC EZ Switch 1024DT. Both are un-managed (plug'n'play) devices.

          Thanks for responding - that's valuable info.

          I may not be able to get to the bottom of this particular issue at this time but with the help I've received in these threads I will definitely be in a better position to understand what may be causing any issues in the future.
          A recent poll suggests that 6 out of 7 dwarfs are not happy

          Comment


          • #6
            Re: Help with understanding why router blocked network

            Unmanaged will not cause the situation I encountered. My issue was a newish feature that was unknown to me ain a managed switch.

            Got a new bale of hay so I can not clutch some more straws when sleep revives what few grey cells I have that still work. Somehow one of the Community will provide the necessary clues or indeed the solution to this conundrum you had.

            80,000+ Members, someone will think of something.
            1 1 was a racehorse.
            2 2 was 1 2.
            1 1 1 1 race 1 day,
            2 2 1 1 2

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            • #7
              Re: Help with understanding why router blocked network

              haha thanks

              If anyone else would like to contribute please do so
              A recent poll suggests that 6 out of 7 dwarfs are not happy

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