AC1200 wifi cable modem router IP address being used by multiple devices

[jenkelly330]

We often cannot connect to the internet. The error message states: "Another device on the network is using your computer's IP address. Try connecting again later.If you continue to have problems, change the IP address of the other device."

We upgraded our internet service with Xfinity from 200 mb to 800mb within the last week and we continue to have this same problem. I called them and they said that I had to contac the manufacturer of the modem as only they have access to renew the IP address. Is it that we have too many devices working and the modem can't handle them all? Do I need to upgrade my modem? I am not techically adept at all and can use some assistance from anyone willing to help us figure this out. Thank you in advance for any help you can provide.

[plemans]

the C6220 (if thats what you have) is only rated to 200mbps for xinity. If you're paying for 800mbps, you'd need to upgrade to something that supports those speeds. 

How many devices are on the network? 

Is it only wired devices with issues? only wireless? 

Devices on the 2.4ghz? devices on the 5ghz?

[antinode]

> We often cannot connect to the internet. [...]

   "cannot connect" _what_ "to the internet"?

> [...] The error message states: "Another device on the network is
> using your computer's IP address. Try connecting again later.If you
> continue to have problems, change the IP address of the other device."

   That's a connect-to-the-LAN problem, not a connect-to-the-Internet
problem.

   That usually indicates a problem with way the devices on your LAN are
configured, not a problem with your router.

> [...] We upgraded our internet service with Xfinity from 200 mb to
> 800mb within the last week and we continue to have this same problem.
> [...]

   Not amazing to me.  If you didn't change anything which might cause
that problem, then I wouldn't expect it to heal itself.

   (Note: "m" = "milli" = 1/1000. "M" = "mega" = 1000000.)

> [...] I called them and they said that I had to contac the
> manufacturer of the modem as only they have access to renew the IP
> address. [...]

   Someone lost the part of that message which might have made sense.

   You router has two IP addresses: One for its WAN/Internet interface,
and one for its LAN interface.

   Its WAN/Internet interface is used to communicate with your ISP.  You
have no control over the address of that interface, and it's not part of
this problem.

   Its LAN interface is used to communicate with your client devices
(wired and wireless). It's address is normally "192.168.0.1", and it's
also not part of this problem.

   Your client devices should have IP addresses like "192.168.0.x",
where "x" is between 2 and 254 (inclusive), and "x" is different for
every device.

   When a device starts up, it tries to configure its network interface
with some address.  Normally it would use DHCP to ask (the DHCP server
in) the router which address it should use.  When it tries to configure
the interface, it first checks to see if some other device is already
using the proposed address.  If it finds that that address is already
being used, then you get a message like the one you quoted.

   One mystery is _which_ "Another device" is conflicting.  The other
mystery is which device is not using DHCP to get its address.

   Generally, the router's DHCP server will not grant the same address
to multiple devices.  So, if there's an address conflict, it's normally
because someone has configured one of your devices with a static address
-- one which was explicitly specified by you/someone, rather than one
which was obtained from the router's DHCP server.

   I know nothing about your devices, or who configured which how, but
you might try disabling some of them to try to determine which one is
causing the problem.  (Your (unspecified) computer could be the culprit,
too.)

> [...] Is it that we have too many devices working and the modem can't
> handle them all? [...]

   Unlikely. How many devices have you?

> [...] Do I need to upgrade my modem? [...]

   I doubt that that would help.

[jenkelly330]

Our laptops are the issue and occassionally the tvs. We have 4 laptops, 4 cell phones, a couple of videogame systems, 3 smart tvs.....We believe, as you suggested, that we need to upgrade to a modem that supports 800mbps. Thanks for your input. 🙂

[jenkelly330]

My laptop may be the culprit since it was confgured by my employer. I don't feel comfortable disabling my work laptop (not sure I would even know how to do that), so I'm hoping that changing the modem to something that supports 800mbps will fix the issue.  Thanks so much for your time and expertise! 

[plemans]

You could always go into your router and set a reserved IP address for the work computer. 

In terms of modems, I'd encourage you to look at a docsis 3.1 device at least. More and more ISP's are requiring docsis 3.1 for lower speed tiers 

[antinode]

> My laptop may be the culprit since it was confgured by my employer.  I
> don't feel comfortable disabling my work laptop (not sure I would even
> know how to do that), [...]

   Shut it down?  I wasn't suggesting using a sledge hammer on it.

> [...] so I'm hoping that changing the modem to something
> that supports 800mbps will fix the issue. [...]

   The modem speed is unrelated to any IP address conflict.

> You could always go into your router and set a reserved IP address for
> the work computer.

   I'd want to know who's conflicting with whom before I started playing
around with anyone.  Reserving an address for some device or other
should be harmless, but might or might not help.