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Solved Cascading Routers - cannot access DHCP via wireless

Discussion in 'Networking' started by plbowers, Sep 14, 2017.

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  1. plbowers

    plbowers Thread Starter

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    I am replacing a defective Netgear router that was working in this same configuration for years. I am replacing it with a TrendNet TEW-731BR (N300 WiFi Router). This router will be used without WAN connection at all - just purely as a wireless AP with the intent that it passes everything through the LAN port to the "parent/master/A" router which has DHCP activated and has access to the internet.

    Quick summary:
    Master - 192.168.1.1 (DHCP is 192.168.1.20 to 192.168.1.254)
    New TrendNet - 192.168.1.9 (DHCP disabled)

    My configuration is a straightforward LAN-to-LAN, same-network type of cascade:
    (start disconnected from everything - just connect via wifi to the TrendNet router)
    * factory reset the TrendNet router
    * Go to the setup page and...
    ** disable DHCP
    ** set the static IP address to an unused IP address outside the DHCP range of the master
    ** change admin password
    ** set SSID and wifi password, change security to WPA/WPA2 AES
    (now connect the TrendNet, newly configured, to the master router LAN to LAN. WAN is not used at all.)

    The computer I was using for configuration now works great. Full internet access, able to ping/access anything on my intranet, etc.

    Any other device hangs on access and ultimately says it couldn't get an IP address. If I set up a static IP address then I can connect with the other devices.

    It's as if the TrendNet router doesn't know to hand the DHCP request over the LAN port.

    I confirmed multiple times that "WiFi isolation" is turned OFF. I thought it might be a bug with off being on in the UI so I tried turning isolation ON and that didn't change anything (surprisingly - I thought I wouldn't have internet access after that) so I turned it back OFF.

    I looked for some kind of "WiFi Access Point Mode" or "Bridge Mode" setting but I'm not finding anything.

    I found a "Wireless repeater" mode and when I set it up then it does work, but it is noticeably slower and it's just pointless to have the ethernet strung and then not use it. Performance seemed noticeably slow on the wireless repeater mode as well (although I have no hard numbers to prove that - just felt unusually slow).

    I have another router coming off the same master in the same type of way but using a different IP address. It continues to work fine.
     
    Last edited: Sep 14, 2017
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  3. etaf

    etaf Wayne Moderator

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    is that the only other device you have connected
    try a powercycle of the main router
     
  4. plbowers

    plbowers Thread Starter

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    Good thought, but no change.

    I rebooted the primary/master and waited for it to come back and then rebooted the secondary/slave/(new TrendNet). My main computer (that I did the initial configuration with and I assume is in some cache) works fine and I cannot connect with other devices still.

    Thanks for the input...

    ===EDIT!===

    Wait - I took a break to grab a sandwich and when I came back one additional device was able to connect. After I connected that one others "fell into line". At this point I seem able to connect with any device, as expected.

    THANK YOU - the reboot turned out to be the solution, albeit delayed for whatever reason.

    ===EDIT!===

    I was on my way to mark this as solved when I noticed another device that was having difficulty connecting. I went back and disconnected and tried to reconnect on other devices and realized that either it was sporadic before or else the reboot has knocked something loose so it's sporadic now.

    I now have little solid to report. Some devices seem to connect instantly (esp the one I did the configuration with originally). Some devices connect quite slowly but fairly consistently. Some devices connect sometimes and fail other times.

    Unfortunately that makes it really difficult to diagnose... Sigh...
     
    Last edited: Sep 14, 2017
  5. etaf

    etaf Wayne Moderator

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    yes that does make it less straight forward

    what if the device is faulty
    do the devices lose ip or just cant get internet

    can you setup like a normal router using its own dhcp - and do devices connect ok and stay connected

    how many devices are you actually connecting up ?
     
  6. TerryNet

    TerryNet Terry Moderator

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    I think that you have multiple wireless networks (plus maybe there are other ones owned by neighbors).

    Does the new TrendNet have a unique SSID and using a channel that is not suffering possible interference from any of the other networks? (The symptoms you report are consistent with wireless interference.)
     
  7. plbowers

    plbowers Thread Starter

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    Certainly possible. Not the answer I want to hear because I'm currently installing this overseas and don't want to have to bother with returning it. But "I don't want to hear it" is not exactly a rational response... :)

    They just can't connect. If a device connects then it invariably has internet, but about half of the devices fail in the connection about half the time.

    Yes, it's a bit difficult because I have to either physical disconnect the 2 routers or else turn off dhcp on the master before turning it on in the slave, but once I do one of those steps (I tried the latter) then the connection proceeds without difficulty. However, this router doesn't have an option to set a default gateway (?! What genius thought THAT would be a good idea for a DHCP server ?!) and so I can't just swap roles and leave this modem in charge of DHCP. But as a temporary solution, yes, it makes it so devices can connect.

    About 5-6 non-interactive hardwired devices (printer, stereo, xbox, old laptop acting as backup server, etc.) and 5 routers/switches total (modem/router A with forced wifi isolation so wifi turned off with DHCP which connects to router B via LAN which connects to a simple switch C which connects to the non-interactive devices and the 2 cascaded routers D&E [where E is the new TrendNet]) and then via wifi to about 12-15 other devices.
     
    Last edited: Sep 14, 2017
  8. plbowers

    plbowers Thread Starter

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    Yes, I OFTEN see neighbor's ssid popping up, but always at a very low signal strength. My own system has 3 separate SSIDs spread throughout the house.

    Yes, all SSIDs are unique and separated by at least a channel or 2. The neighbor signals do overlap, but the difference in signal strength (theirs barely registering and periodically dropping out entirely while mine are at top strength) has always led me to believe I didn't have to worry about it.

    I have currently disabled another wireless radio so my 2 signals are on channels 7 and 11. One neighbor is particularly strong today, but he's on channel 5. All other neighbors that creep in and out are down in the 1-5 range.

    I do note that I just recently turned on a Disney Circle device but haven't set it up yet. When I was just looking at the wifi analyzer I noticed that it was overlapping with the TrendNet so I have now turned that device off entirely. I'll see if that helps.

    ===EDIT! [specified channels above]===

    No change based on turning off the Circle device.
     
    Last edited: Sep 14, 2017
  9. TerryNet

    TerryNet Terry Moderator

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    OK, but remember that the only completely non-interfering three channels (in the US) are 1, 6 and 11.
     
  10. plbowers

    plbowers Thread Starter

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    I changed things around so I just had the 2 connected with the new one on channel 11 and the old one on channel 1. Various neighbors come in around until channel 5 but no higher.

    Same behavior.

    I tried with just the new one connected. Same behavior.
     
  11. etaf

    etaf Wayne Moderator

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    So the router is happy connecting those devices

    can you give the settings details
    IP address
    DHCP range on main router
    gateway IP
    etc
     
  12. TerryNet

    TerryNet Terry Moderator

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    I assumed that you are talking about the LAN IP address being 192.168.1.9 and the LAN Dhcp server being disabled.

    If you were talking about setting the WAN IP address to static instead of dynamic that is surely the root of your problems. I doubt this is the case, but I'm desperately trying to find something here. :)
     
  13. plbowers

    plbowers Thread Starter

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    Unfortunately for the purposes of diagnosing that isn't the case - I have not touched either the WAN ports or the WAN settings as I see them as being irrelevant in my setup... Sigh...
     
  14. plbowers

    plbowers Thread Starter

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    192.168.1.1 is the modem/router with the wifi radio turned off. It controls DHCP with a range of 192.168.1.10-254 and a gateway of 192.168.1.1 and DNS of the same. It has a single ethernet cable leaving it connecting it to the 8-port switch.
    The 8-port switch is hooked up to...
    (1) 192.168.1.2 is a router with DHCP turned off
    (2) 192.168.1.3 is a router with DHCP turned off
    (3) 192.168.1.9 is the new router with DHCP turned off
    (4..8) printer, backup "server", stereo, etc.

    The new router doesn't support specifying a gateway other than itself via its own DHCP (crazy!) so previously I was thinking that I couldn't use it as the DHCP server (in a single subnet the modem/router HAS to be the gateway). However, I just realized I could put it BETWEEN the modem/router and the switch, hooking it up to the WAN port on the TrendNet. This would isolate the modem/router from the rest of the network, but now that I think of it there's no reason why not to do that...

    It's definitely a "workaround" rather than a "fix" but I think I'd be satisfied with that at this point if I could have a working network again...
     
  15. plbowers

    plbowers Thread Starter

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    YAY! I think the workaround has figured it out. Now I've got a (tiny) subnet between the WAN of the new trendnet router and the modem and everything else is on my usual network (haven't checked sharing yet, but I am pretty hopeful). The TrendNet (power hungry maniac that it is) now has the DHCP authority it has been craving and finally seems to be behaving. All 3 wireless routers seem to be accepting connections and handing out DHCP without complaint. I have to figure out a new placement because this places 2 routers closer than they should be, but I've got them on widely separated channels so even in the near term before I move one I think I should be OK.

    Thanks for your time and expertise and help!

    On a separate note, and for your viewing enjoyment, I have attached a screenshot of my "connect to wifi" screen on my phone. You will note that I have teenage boys who take a somewhat gleeful interest in naming our SSIDs. Here's the write-up of this whole process (that y'all have contributed so much to) that my 13-year-old boy wrote up yesterday mid-process...

    Due to the thick, concrete wall construction of our house we have 3 separate routers spread around in different rooms for our wireless signal. We have named our wireless routers "Connected.", "Connecting...", and "Disconnected.". Yesterday we connected connected, but then due to technical difficulties, we had to disconnect connected and connect connecting so we could stay connected. Unfortunately despite hours of work connecting doesn't connect, so tomorrow I will disconnect connecting and reconnect disconnected and make sure connected is connected. In short, I connected connected, then I disconnected connected and connected connecting, but that didn't work so I disconnected connecting and reconnected disconnected. Although connected was the original connection problem, tonight disconnected unexpectedly disconnected and seemed like it would never connect again - fortunately a few hours later disconnected spontaneously reconnected from its disconnected state.

    After many hours of blood, sweat & toil (much of it yours here on this forum!) I am happy to say that Connected, Connecting, and Disconnected are all connected and we as a family are fully connected once again.

    THANK YOU!
     

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