Networking Guide: Part 4 - Finding Your Network’s DHCP Range

Sep 20th 2018

Networking Guide: Part 4 - Finding Your Network’s DHCP Range

Description

Part 4 of our Networking Guide demonstrates the process of finding your network's DHCP range.

Transcript

Welcome back to ApexCCTV’s video tutorial series on port forwarding, this is going to be a simple video on how to find your routers DHCP range. That’ll be extremely important when selecting an IP address for your router.

If you don’t know, DHCP is a protocol for new network devices to acquire a new IP address from a router, a DHCP server can run a lot of places, but in the most common home and small business scenario’s’ we run into its typically going to be a router running that. Of course we are going to log into that with our internet browser. I’m going to type in my routers IP address and login and now I’m looking at the user interface for my Netgear router that I’ll be using today.

Almost without fail the DHCP range will be found on a page that says LAN set up, LAN configuration or just LAN. It’s usually in a basic menu. It’ll be on the same screen as you can set a static IP address on the LAN side. For this router it’s on the bottom of the menu under advanced and it’s on the page that says LAN setup. This is where I set up my basic local area network configuration for the router. I’ve given it a static IP address; it’s on the same subnet mask as the rest of my network, so this is all ready to go. 

You can see I have my “use router as DHCP server” unchecked because we have some pretty advanced net settings around here for all the videos we’re creating, but if it were checked my DHCP range is always going to start with the first 3 octets of my LAN setup. What this means is when the first new network client connects to the router for an ip address its going to get .100, and count up from there and if you have a really big network it may go all the way up to .254.

The reason this is important to know about is if you are in a situation where you have selected a static IP address for a DVR and its inside the DHCP range, say I put the DVR on 192.1968.1.105, well as soon as I get a 6th network client the Netgear router will, not knowing that I’ve set the DVR up as a static IP address will go ahead and reassign that .105 to the new device. Now we have an IP address conflict, two different devices on the same local area network segment trying to share an IP address. What that does is effectively break the network connectivity for both devices; no network, no browsing it from another computer no seeing it on the internet, no nothing. Neither one will work properly.

So just some note taking when you go to set up a network device that is going to have a static IP address is to figure out what the DHCP range is. A real common scenario for installers is that the DVR has been put on the network as DHCP and say it picks up .101 and they’ll just go into the DVR’s network settings and change it to static and leave the rest of the settings alone. That’s a big mistake because the next device that comes on the network will cause problems and it will inevitably happen a week after you’ve finished installing and then you’ll have to reroute all the port forwards and everything else you configured in that router.

Just figure it out up front and make sure you pick an IP address not in this DHCP range, .10 .20 are fine, anything .100 or over will cause you problems.

That concludes our tutorial on finding the DHCP range of your router, we hope you’ve enjoyed it and check out the rest of our videos at www.apexcctv.com.