Is this a modem problem or is it something else? Need help.

Discussion in 'Networking & Security' started by supo, Dec 31, 2019.

  1. supo

    supo n00b

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    Hi all, I don't know what to think of this problem of mine I'm having now. So my issue is that my internet drops/becomes extremely unstable after a few days of usage randomly. When it happens, I can barely open a webpage on my PC, or any other device. I got a new and upgraded modem/router combo from my ISP at home last month but I'm using my own private wireless router (newly bought Asus ac86u) and every device is connected to this router, and the router is connected to a switch as well for more ethernet ports usage.

    When the problem occurs, I have to restart the modem/router then it works good again. However if I restart my own Asus router, the connection works again too, tried this only once though so it could be a coincidence. And another thing I've noticed is that when I lose internet connection I cannot access the configuration UI of the modem/router at all. I have tried different routers as well also but still the same issue.

    If there was a problem with the modem/router why does restarting my own router temporarily also fixes the problem? I've Bridge mode activated as well so everything should be good, cables etc are all good too. I have a 500mbit down 200mbit up connection btw and I do get full bandwidth from my ISP, however once the internet starts becoming unstable and I do speedtest the down and up speed are much lower and just random. Can DHCP cause a conflict and kills the connection or something maybe? I have DHCP reserved just my PC, every other device is automatic DHCP.

    I didn't have this issue before on my previous modem/router from my ISP, and the reason they gave me a new one is because they "upgraded" the lines in the neighborhood so everyone got the same model/router etc. I asked a few neighbors but they don't experience the same issue like mine. There are no overheating issues btw.

    Any suggestions?
     
  2. Kardonxt

    Kardonxt 2[H]4U

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    I would start by taking the ISP combo unit out of bridge mode and using its router functionality \ removing your personal router. If the problem goes away then you know it's your personal router. If the problem persists then there is something wrong with the ISP or Modem \ Router combo.
     
  3. supo

    supo n00b

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    Okay it happened again now. So this is what I did to troubleshoot, and I really can't find the root of the problem.

    First of all this is my setup: ISP modem/router(in bridge mode) ----> Asus ac86u router ----> network switch Netgear with 8 ethernet ports that I use.

    One single ethernet cable goes from modem/router to Asus router, Asus router have 4 ethernet ports and they are in use by other devices, then one ethernet cable goes to the switch from Asus router and almost all the ports on the switch are used by other devices as well.

    So when the problem occured again this is what I did:

    I disconnected the Asus router and connected my desktop PC directly to the modem = internet worked again without problems with full bandwidth as it should be
    Then I again connected the Asus router to the modem/router and my PC to the Asus router = internet worked again without problems with full bandwidth as it should be

    So I didn't need to restart neither my Asus router nor my modem/router combo. At first glance it would have seem that it's a router problem however I have tried several routers at home, and with all of them it's the same issue. There is a conflict going on somewhere that is my best guess, but what can cause such a thing? And another thing, is it normal that I have two IP addresses? Because my Asus router shows one IP, and my modem/router shows another IP? Can there be a conflict in such a thing?

    Also can it be that an ethernet cable is bad somewhere that can cause it?
     
  4. jardows

    jardows [H]ard|Gawd

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    Yes, that is a distinct possibility, and I have ran into that on several occasions causing intermittent connectivity.

    You may also want to check the default IP address of the combo unit provided by the ISP, and the default IP address of your router. Even in bridge mode, there can be some conflicts.
     
  5. BudgetBuilder

    BudgetBuilder n00b

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    Make sure they they both have different LAN addresses. Also a bad switch can cause this problem.
     
  6. Dead Parrot

    Dead Parrot 2[H]4U

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    Did the problem start with the arrival of the new ISP router/modem combo? Or when the new Asus was added to the mix? Always suspect the new thing if something working starts not working.

    Might not be a bad unit, could just be a bad configuration.

    Are the units on a UPS? Separate electrical circuit? If shared, maybe a new non computer device is causing a short power drop/spike that resets one or more of the network devices.

    Rarely a bad idea to swap cables when chasing intermittent connection issues.

    Make sure you have only one device trying to be a DHCP server.
     
  7. supo

    supo n00b

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    Yes the problem started with the new arrival of the modem/router combo. I've tried different wireless routers I had at home from before so with all of them the same thing is happening. However I also bought the new Asus ac86u to make sure that at least I have a new and good wireless router. The modem/router and my own Asus router are on the same UPS yeah but that has always been like that in the past as well with my previous modems. My other devices, like PC etc are on different rooms and cicuits etc.

    When it comes to DHCP I use my Asus router as the server that gives every device automatic IP, just my PC I assigned a manual one.

    What I didn't try is to factory reset the modem/router that I got from them, maybe it can help somehow hopefully. However in this particular case of mine though, how can this issue occur after exactly same amount of days? It's like there is a countdown somewhere and after so so many hours/days it happens, in this case 3 days.

    The switch I'm using is an unmanaged one, so everything is automatic, been using it since 2014 without any issues at all. However if the switch became bad somehow, then wouldn't I notice it right away with the connected devices on it? I'm not sure..
     
  8. Dead Parrot

    Dead Parrot 2[H]4U

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    After doing a restart, check the DHCP lease time the new router is getting from the ISP. Make sure it isn't 3 days(or whatever your good working time is). Maybe the renewal isn't working properly. Same for the IPs handed out by your new Asus router.

    Switches, especially the cheap ones, can fail in weird ways. I had one that would work for a while, then stop. The indicator lights would keep flashing just like when it was working only no data was being passed. Only found that when I swapped switches when it had failed and things started working again.
     
  9. supo

    supo n00b

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    How can I check though if the renewal of leases causes a conflict or something? On the Asus router (both the new one and the previous one I had) it is defaulted at 24h lease times, and never had any issue with it. I have like around 13 devices that connect to the router at home, 24h should be more than sufficient no? I have also checked every ethernet port on my switch and all of them seems to work fine without issues.
     
  10. BudgetBuilder

    BudgetBuilder n00b

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    I had a couple switches that would overheat and do something similar. I removed the top of the case and installed a fan and never had another problem.

    I have also had switches that if i had to guess were trying to route to the wrong ports. As soon as i restart the switch the problem went away.
     
  11. Dead Parrot

    Dead Parrot 2[H]4U

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    My thought was the lease might be set for 3days and failing to renew, causing your problems. You can double check by changing your lease times to 1 hour and see if the problems happen a lot sooner. (a 24h lease should not be a problem once you get things fixed.)

    Do an ipconfig /all (windows dos box) and verify the dhcp server is correct in case some device has decided it is a dhcp server in addition to your proper one.
     
  12. Nicklebon

    Nicklebon Gawd

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    Router crashed and rebooted.
     
  13. Mega6

    Mega6 2[H]4U

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    your router is definitely rebooting itself. update your firmware to the latest. dont publish photos of your logs with the ips. blur it out.
     
  14. supo

    supo n00b

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    Actually it was me who rebooted the router so that my connection will work again. It is updated with the latest firmware, also it's a brand new Asus router ac86u, and like I said the issue happens with three different routers I tried. Restarting the modem without restarting the router also fixes it. Also restarting neither and just unplugging and plugging the ethernet cable behind the modem also fixes it. I cannot isolate the issue that is my problem.

    I didn't know how the log looks like when I reboot the router so that's why I thought something else fishy going on looking at the logs.
     
  15. Mega6

    Mega6 2[H]4U

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    its a modem issue then and have the cable company replace the modem and/or fix the issue. they should run signal tests as well.
     
  16. BudgetBuilder

    BudgetBuilder n00b

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    Put an unmanaged switch between the modem and router. The first time it happens unplug the cable going into the modem and see if it still resets. Next time do the same thing with the cable going into the router.

    This should let you isolate which port is being reset by unplugging the connection.
     
  17. Nicklebon

    Nicklebon Gawd

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    Are you hard coding link speed between router and bridge?
     
  18. supo

    supo n00b

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    Umm I didn't understand what this means? What is hard coding link speed?
     
  19. Nicklebon

    Nicklebon Gawd

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    Setting the speed and duplex ie 1000/full.
     
  20. supo

    supo n00b

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    No not doing such thing, just an ethernet cable from the modem to the router while the modem is in bridge mode.
     
  21. stormy1

    stormy1 [H]ard|Gawd

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    Replaced the cable between the router and the asus and between the switch and the asus?
    I have come accross a ton of defective cables bundled with modems and routers.
    At one time it was so common that I just tossed them unused and used monoprice cables.
     
  22. supo

    supo n00b

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    I think I just found out that this is exactly the problem. Ok so first of all I changed my ISP modem with a new one just to make sure that it's not an hardware issue. However the connection issue happened again after 2-3 days and then when I checked my Asus routers log I see this:

    "dhcp client: bound 84.210.xx.xx/255.255.240.0 via 84.210.xx.x for 188821 seconds."

    188821 seconds is roughly 52 hours, so this must be the exact duration of my internet working properly until it becomes unstable. The ISP's modem cannot renew the DHCP of the Asus router properly then? How can I fix this? I've checked all the settings of my ISP's modem but I cannot find an option where I can adjust DHCP lease times etc.
     
  23. Mega6

    Mega6 2[H]4U

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    what are your wan settings on the asus? Automatic IP should be set there. NOT STATIC

    upload_2020-1-23_16-57-40.png
     
  24. supo

    supo n00b

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    WAN Connection type is set to Automatic IP yeah. It's like that by default.
     
  25. Mega6

    Mega6 2[H]4U

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    so you need to check your lease time and see if it expires and you end up with an expired ip. I would put the router in bridge mode and let the asus router handle the ip/renew. It works well that way, not sure why you would have an issue with automatic. Do you have to login for access? Such as ppoe?
     
  26. supo

    supo n00b

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    Yes I put ISP modem/router to bridge mode however it didn't solve the issue it's still happening. The Asus router is handling the renews however the problem it seems is caused by that the Asus router cannot get a renewed IP after the lease time of 52 hours is over.
     
  27. Mega6

    Mega6 2[H]4U

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    Then put the isp router in a normal node, disable dhcp on the isp router and find out what the default isp router subnet is. hardcode your asus to one of those subnet ips. Your gateway for your asus route will be the isp router. the gateway for your clients will be your asus ip.
     
  28. supo

    supo n00b

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    So after I do all these, i should not put the modem back into bridge mode again?
     
  29. Mega6

    Mega6 2[H]4U

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    correct, because from what we can tell.. bridge mode isn't working on dhcp renew. let the isp router handle the wan dhcp. hardcode your wan on the asus and the clients to the proper subnet/gateway. let me know if u need help. However, your ISP should be helping you with this - it's their issue/stuff, That's what you pay them for. Regardless, I am hear to lend a hand if they keep you hanging.
     
  30. supo

    supo n00b

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    Thank you very much, I will do it after I come home later today, at work atm. Will let you know if I'm stuck during the process.
     
    Mega6 likes this.
  31. Mega6

    Mega6 2[H]4U

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    ok,

    Call your isp and tell them that your asus router is not renewing ip with their router in bridge mode. try and make it their problem. More than likely, they will say just use their garbage router. At least give it a shot. Also make sure/check that they are not using ppoe something to renew with. If they are, just setup the asus with the auth.
     
  32. supo

    supo n00b

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    Will do. My ISP's modem/router is this one btw Sagemcom Fast 3890V3. The previous model didn't cause any issues but like I said they gave me this new one November last year after they upgraded the lines.
     
  33. Mega6

    Mega6 2[H]4U

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    Ah, sagemon. I've seen those junkers around. Some isps usie ppoe and have login creds. So in bridge mode, I have those creds in my asus. have the isp run a signal test and diagnostics to confirm your signal is good.
     
    Last edited: Jan 24, 2020 at 1:16 AM
  34. supo

    supo n00b

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    Btw a quick question; would putting an unmanaged Switch between the modem and my router solve the renewal issue?
     
  35. Mega6

    Mega6 2[H]4U

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    You shouldn't have to do that. As long as your wan ip shows up in your asus and your isp modem is in bridge that's all that needs to be done. Along with any cred info for ppoe or whatever as / if required by isp.
     
  36. supo

    supo n00b

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    Yeah I see. However running my ISP's modem/router without it being in bridge mode will not cause any conflicts with my Asus router?
     
  37. Mega6

    Mega6 2[H]4U

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    It will be a pain in the rear to setup as it will be double nat, a default route setup and a new subnet. UNLESS maybe we can put in a DMZ if the router has that. So your ISP would be really the way to go to get them to fix their stuff.
     
  38. supo

    supo n00b

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    Yes I see. However I'm just wondering how they can fix it though? I mean what do they have to do technically so that dhcp renewal is working properly?
     
  39. Mega6

    Mega6 2[H]4U

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    1) as mentioned previously - signal check
    2) isp router firmware/firewall check to make sure that bridge mode works and passes the wan ip properly to the asus.
    3) YOU have to check and make sure with isp what mode to set the asus in and if you need ppoe creds.
     
  40. supo

    supo n00b

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    I did call them two weeks ago, they did a signal check and all was fine however when I put it back into bridge mode the guy on the phone said he could not access the modem etc

    As far as I know I don't need any ppoe creds, never needed all these years and it was working flawlessly.

    Edit: all they are saying on the phone are basic things, factory reset your modem or router, power cycle bla bla.