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Is my technicolor DPC3216 modem resetting my Linksys router's IP ?

marklynmarklyn Posts: 64
in Connectivity Jun 22, 2020

Lately, within the past 2 months, my router's ip has been reset to a 10.xxx.xxx.xxx number from my original setting. This has happend 3-4 times now and at the time it occurs I'm not doing anything other than light surfing and in some cases I'm not even home.

I read on a linksys thread that this happened to someone else with a linksys modem and a cable modem that has wifi/router capability but that was turned off.  (see here) My cable modem doesn't have that, it's just a straight cable modem.

My fix, once I discovered it, is fairly simple. I just use my phone to connect to the router wifi, login, and manually change the router's IP back to the IP i've always had it to.

Does anyone here think that somehow the cable modem could be related to the problem?

I've reset the router back to factory twice and set it back up, that didn't fix it and this seems to be very random as far as I can tell (no power outages, etc.)

One last note, I recently set my router's subnet from to to be able to "find/search" for new cameras I purchase with an 192.168.1.x IP address. Not sure if this could be related to my issue.

My router is a linksys WRT1900AC by the way. 


  • RAIST5150RAIST5150 Posts: 646 ✭✭✭✭
    Jun 22, 2020
    Are adress changes occurring on both the WAN and LAN side, or just one of the interfaces?

    The WAN side (uplink) can change anytime the lease is renewed from the Spectrum servers.

    As to the LAN side, Spectrum would only make changes there if they are managing your wifi and such.

    If it is your own router and you changed the credentials away from the factory defaults, they would not be making changes unless you granted them access with those new credentials.

    In the short term, change the passwords for the router (wifi and admin) and verify there are not any unwanted/unknowm devices connecting to your wifi.

    May also want to run some malware scans on your devices.
  • marklynmarklyn Posts: 64
    Jun 22, 2020

    No address changes are occurring on the LAN side for sure and if Spectrum changed because of a lease expiration, I don't think that's it since this happened twice in one day and has been happening in the last couple months, maybe 1-2 more times.  I manage my own wifi and have everything setup with static ip's. I have strong credentials, former IT career, so I'm confident no unwarranted entry was done to my router. I monitor stuff frequently, keep my Bitdefender updated and occasionally restore my system from a clean image when I feel the time is right, usually every couple months or so.

  • RAIST5150RAIST5150 Posts: 646 ✭✭✭✭
    Jun 22, 2020
    Sounds like you are seeing their internal private address space used on the other side of your WAN interface, which can change with lease renewal. Used to see that address space referenced on some of my old Motorola modems.

    That is part of their network structure on the "public" side of your connection--it would be mapped to the publicly routable address and such on their end. It shouldn't have any impact with what you are doing on your LAN side, as it is on the other side of the WAN interface (unless perhaps you try to link to an IP that exists in the same subnet of both interfaces, and it is down on the LAN side?).

    You should not be manually setting the IP/subnet/gateway paremeters on the WAN side unless support is telling you to do that specifically. It can cause a conflict if they try to issue that IP to someone else. It needs to be set back to the automatic config settings.
  • marklynmarklyn Posts: 64
    Jun 22, 2020

    Sorry, I think you misunderstood me.

    I'm only setting IP/subnet and/or DHCP adressing on my side, I'm not doing anything on the public (their) side, in fact I don't have a way to login to that modem.   While I don't see how anything on the modem could interfere with any IP settings on my (LAN) side, I referenced a post in my original post about such an event thinking that maybe there is something going on I'm not well versed in.  I've had this modem/router setup for a couple of years so I don't understand why it's doing this now. It's not like I change setting often because I don't.  The only thing I recall changing on my router is the subnet as mentioned in my previous post and I only did that because I can access default IP camera addresses to manage them since they usually come with a 192.16.1.x address.

  • RAIST5150RAIST5150 Posts: 646 ✭✭✭✭
    Jun 23, 2020
    Talking about the WAN interface of your router, nothing to do with you configuring the modem.

    You said there were no changes happening to the LAN side... which sounds like you are seeing changes happening to the WAN interface of your router. This should be set to auto configure and can change if Spectrum makes changes on the modem's side.

    Again... this is all talking about the scope of things occurring on the WAN side of the router--the uplink side that Spectrum controls.

    Your modem (and by extension the WAN interface of your router) does not necessarily have to get a directly public IP. It can be assigned an address in any of the private address spaces (192, 172, or 10 for the first octave), that gets mapped to a public IP. This is all done on their side of the equation, and your router should be auto configuring the WAN network connection parameters with the modem. So, if Spectrum changes the modem's address to say, you might see that address get referenced somehow in the scope of the WAN side of things, either in the modem status/log pages or those of your router.

    Depending on how everything is set up, you may never see their internal private address space referenced. As I said earlier, I sometimes saw it referenced back when I used Motorola modems. Never saw it when I later started using my own personal Zoom or Netgear modems (have always used my own routers).

    You should be leaving the WAN settings of your router set to autonconfig or you may create problems... if not for yourself, potentially for others.

    Now, if something is changing settings for the LAN side of your personal router, and Spectrum has not been granted access to those settings to make such changes... something may be amiss with security that needs to be ferreted out. A "simple" first step would be to change those credentials in an attempt to block that intrusion.

    May have a sort of visual demonstration.
    This is a demo that is out there on the web... hosted via a publicly routable IP address.:


    Click the circular icon for Primary WAN to view it's status, and you see it is using address in the private space. This is mapped to a public IP elsewhere, upstream from this router.

    Now, along the left pane, click the links for the LAN and WAN interfaces. Note that the LAN page has settimgs for setting up the local network space, which is established as a different subnet space that also starts with 192. Note also the WAN page is set to auto config.

    This is the framework your router should also be following.
  • marklynmarklyn Posts: 64
    Jun 23, 2020

    "You should be leaving the WAN settings of your router set to autonconfig or you may create problems... if not for yourself, potentially for others."

    You're talking about the type of internet connection under internet settings tab, right? Which is and always been set to Automatic configuration - DHCP.

    It would be extremely unlikely that someone or something is doing someing on my side (LAN side). I regularly change pw on my router and access point and they are strong passwords. Since the problem began I've changed the password again about 2 weeks ago and have factory reset the router, also did a configuration restore from a backup made about 9 months ago.


  • RAIST5150RAIST5150 Posts: 646 ✭✭✭✭
    Jun 23, 2020
    I edited in a sort of demonstrstion of things at the end of the previous post.

    What exactly are you seeing change to a 10 based address space?

    If it is changing across the WAN interface, that would be because Spectrum changed the MODEM's interface (or is doing a big revamp of their network structure), and the router changed to match a new configuration. This would be normal... some almost never see it change, but it can for various reasons. For example, I have seen them move me to completely new subnets (altering my geolocation in the process) while they worked on the market's infrastructure. They have also done this in an attempt to get around major routing issues with Level3 before as well.

    If it is changing on your LAN interface , someone/something is gaining access to your router's config. That, or something's triggering a reset (auto firmware update or something?), and the defaults are to use something different from the usual 192 private space.
  • marklynmarklyn Posts: 64
    Jun 23, 2020

    I *think* that the framework for my router is the same, but I may be a bit in over my head.

    I can't see anything changing on the WAN interface. Unless I misunderstand you, I don't really know where to see if/when something changes on Spectrum's side

    The only thing I'm seeing change is the equivalent of the LAN IP on the LAN tab for the site you sent me.  If, as the example, the LAN  IP should be set to then it's occasionally changing to 10.xxx.xxx.xxx (I didn't write down the entire IP address, just know it always starts with 10).

    Hope this helps but I'm still weaving in the dark a bit so maybe I'm not following your line of questioning or thinking.

  • RAIST5150RAIST5150 Posts: 646 ✭✭✭✭
    Jun 23, 2020
    Than something appears to be changing your LAN configuration.

    Which means someone/something may be getting elevated access to that router.

    If admin access is not granted across the WAN interface, then Specrum would not be changing the LAN config. It would have to be accessed from the LAN side (barring some form of hacked exploit). Even if you have allowed external access, Spectrum would still need the proper login credentials to get in... which I am guessing you have changed from the Linksys defaults?

    Of course, that alternate theory can apply as well if your modem is a modem/router combo and it is getting set as if Spectrum is managing the wifi/LAN settings of that combo unit, and your router is running into a conflict. Same thing may happen if you are trying to integrate an access point elsewhere in the house... create a conflict and things go haywire.

    Spectrum would only be changing things on their side of the equation. Their hardware... not yours. So if something is changing on the LAN side of your device, it is a problem occurring on that side of the equation.
  • karlbeckmankarlbeckman Posts: 2,206 ✭✭✭✭
    Jun 23, 2020

    There are added regulatory limitations when you use a Spectrum-provided eMTA modem for digital phone service which includes 9-1-1 access.  The FCC requires the phone service provider (Spectrum) to furnish and have continuous unobstructed access to the modem device at all times.  The subscriber is not permitted to change factory default network access passwords or any other modem operating parameters including network IP addresses.  If Spectrum's firmware tells the LAN port to power up with IP address the FCC says it has to stay there. 

    You ARE permitted to change network IP address parameters in the customer-provided and managed devices you install on your Local Area Network beyond the modem's ethernet LAN connector.  This includes IP addressing structure for your router, cameras, and computing devices. 

  • marklynmarklyn Posts: 64
    Jun 23, 2020

    I'm not sure how any of what I've conveyed in the original and last posts gave anyone the impression that I had changed or had access to change IP settings on the modem but that has never been my issue.  Whatever settings that are on Spectrum's cable modem, I cannot see or access.  I'm only talking about my personal router.

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