Our shared internet network goes down when our friend who pays for a unlimited LTE plan leaves. His phone is essentially the main router. However, recently we decided to create a local network aswell. At this point, I've set up our secondary router (Linksys WRT54G) as an access point. However to do that, I had to disable the DHCP. Is it possible to enable DHCP when the internet connection when the main router goes down, so our devices automatically get assigned IP-Addresses?

In short: Phone (LTE) (used sometimes for internet access) -> Linksys (Either for just LAN access or internet AND LAN access) -> Devices When the phone is gone, the Linksys should start assigning IP-Addresses, since the phone can no longer do it.

  • If I’m understanding you correctly, you and a group of others connect to a WiFi network provided by a friend’s cell phone for internet access. When that friend leaves you and a group of others connect to a different WiFi network without internet access so you can continue to have a LAN for the computers to use. If that is the case why did you have to disable DHCP? Turn it back on. – Appleoddity Dec 9 '18 at 15:33
  • Maybe you are suggesting that you have all your computers wired to the Linksys and they additionally connect to your friends LTE hotspot via wireless? Please edit your question and clarify all of this. – Appleoddity Dec 9 '18 at 15:41

Setup the DHCP servers on the phone and the router to be on the same network segment but have separate IP ranges, so no conflict arises between the two.

In that configuration, whatever DHCP server assigns whatever IP address, the network will continue to function with both or with just one of the two DHCP servers.

  • Sorry for the for downvote, but having 2 DHCP servers acting as primary us never a great idea and this does not actually solve the problem of having an Internet connection where available. – davidgo Dec 9 '18 at 22:58
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    @davidgo: The DHCP server does not need to be the same as the Internet gateway. My own understanding is the problem is that without the phone router they lose network connectivity (but I can be wrong). Otherwise, it doesn't make sense to use a phone as router when a real router with Internet connection exists. The post could be better phrased, though. – harrymc Dec 10 '18 at 7:51
  • Just to clarify, if my main router assigns ip address from .20 to .100, and my secondary router from .80 to .180, but the ip addresses .80 to .100 aren't in use, will they still conflict? And how would I define a static ip address for certain devices? – Simon V. Dec 10 '18 at 11:16
  • No overlap is better, like 10-130 and 130-250. If both routers are on the same network, say for example 192.168.0.x/24, then there is no need for static IP. But if you opt for static IP, this depends on the individual device and its operating system, so there is no one answer, but google is your friend. – harrymc Dec 10 '18 at 12:14
  • @harrymc you are correct, however the DHCP server does need to define a default gateway and prosumer routers tend to assign themselves as the gateway in DHCP - and this can't always be changed. If you have a second device which does not specify the gateway correctly when the gateway is available they still won't be able to talk on the Internet. – davidgo Dec 10 '18 at 14:13

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