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My modem/router (it acts as both) has an IP of 192.168.0.1. The subnet mask is 255.255.255.0. The range of IP addresses used for DHCP is 192.168.0.100 to 192.168.0.200. To be clear, if I connect with DHCP, I can connect with no issue.

I'm attempting to set up static IPs for some of my machines, and I'm running into a strange issue. If I set a static IP outside of the range used by DHCP (such as 192.168.0.66/24 with gateway 192.168.0.1), I can't connect. From my Windows 8 PC, it shows up as "limited", and I can't connect to anything (or even ping the router).

If, however, I set a static IP that's inside the range used by DHCP (such as 192.168.0.166/24 with gateway 192.168.0.1), it will connect with no problems. The subnet mask is not wrong.

This happens whether I use Wi-Fi or Ethernet, and I've looked around in the web interface for my router, and tried temporarily disabling the firewall (no change), and I've power cycled the router and even reset it to factory defaults (again, no change). It is not limited to my Windows PC; every device I have that I can set a static IP on shows the same behavior.

I couldn't find any other settings in the web interface that seemed relevant, and I've never had a situation like this (but, I'll admit I'm kind of a noob when it comes to networking), and I'm out of ideas. For now, I just set the IP to the upper end of the range, and I'm looking into switching out the modem/router, but does anyone have any idea what the problem could be?

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    Most home gateway routers set their NAT (NAPT) gateway to allow a full /24 subnet, and set their DHCP lease pool to a subset of that, to leave some addresses for static/manual use. However, it's possible that your particular model limits its NAT gateway to the same range of addresses as the DHCP lease pool.
    – Spiff
    Commented Feb 5, 2017 at 0:57
  • You might want to advise the model and firmware of your router - it sounds like its doing something a bit non-standard with respect of firewalling/blocking IP's - either that or there is a netmask issue on the router configuration - but, yes, from what you say, this is not normal behaviour.
    – davidgo
    Commented Feb 5, 2017 at 3:27
  • Kevin Mills, it seems you have a good grasp of networking, and your expectations seem accurate. I suggest that @Spiff is right. In theory, a router will listen to traffic of the subnet it's on. But a router could be configured to route, or not route, based on whatever criteria the router decides. So if the router wants to only route traffic from the DHCP pool, that is possible. Your most likely fixes seem to be these two options: either cooperate with the router's observed behavior, or keep focusing on the router.
    – TOOGAM
    Commented Feb 5, 2017 at 7:02

1 Answer 1

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The best way to accomplish what you are trying to do is setup the router "reserved" static addresses for the machines you want. That way it will still use DHCP but it always adding them the same IP you chose. You usually do this where you see what machine has what IP, and you have an option to reserve that IP for that machine.

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    I ended up switching out the router, and everything's fine now, so it doesn't really matter, but my old router didn't support DHCP reservations.
    – Kevin Mills
    Commented Feb 9, 2017 at 0:44

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