BLUF (Bottom Line Upfront): If You are Having Issues Suddenly with your Router NOT Assigning IP Addresses... Check and Change your DHCP Lease Time.
- Advanced Settings Tab
- Setup
- LAN Setup (Scroll to the bottom)
- DHCP Lease Time (range: 1-24 hours)
DETAILS:
This morning when I woke up there had been a power drop in the evening and now I could not access the internet on any device. Full transparency, I have a smart home with 170 connected devices. I really only use the NH for DHCP as I have a 3k SF, multi-level house and the devices that use WiFi do so via 1 of 3 access points that are load balanced. All computers and anything that can use hardline... do. After most of the day hunting the net-demon, I narrowed it back to the NH itself. I was pretty sure I was not getting DDoS'd and my wifi radio signal does not go beyond my driveway. I have one in-range neighbor who is NOT a techie. After a full nuke and pave of the access points AND the NH, I managed to get the hardwired computers back and OCCASIONALLY some of the WiFi.
When I was ready to just junk the device and go a different direction... I figured it was worth a shot to TRY the Netgear support - even though I knew I was outside of my support window by a month.
As I was explaining the issue to the tech and presenting him my data points, I came to one data point. My iPhone. The NH was showing it as having a valid IP... but the phone was showing no connection AND a self-assigned. Then I remembered a client of mine from many lifetimes ago. A husband and wife who ran separate conjoined businesses with good-sized staffs. They were having this exact same issue. The problem turned out to be long leases on DHCP.
The NH, by default, has a 24-hour lease. If you are a "normal" user... this would likely never be an issue. But... if you are a "power user" or a business trying to use "home gear" where at very least you should be using SMB (Small-Medium Business) gear. You MAY, at some point, run into DHCP lease issues.
I dropped my leases from 24 hours to 1 hour and instantly my problem resolved. Now to figure out what the best time frame is?
The key take away is: Short DHCP lease time has some advantages, especially for networks that have a high turnover of devices or a limited pool of IP addresses. Long DHCP lease time also has some benefits, mainly for networks that have a stable and predictable number of devices or a large pool of IP addresses.
Back to my situation. Remember, I have 170 network connected devices - on IPV4. That means I cannot have more than 255 devices in that IP range. Remember also that I mentioned the power thing. If I have 170 devices, all with 24 hour DHCP lease holds and most of those are non-static IoT devices, a power outage COULD result in 100+ devices "asking" for an address - again. If just 100 of my 170 did that... I would be at 270 and over the 255 cap in a snap.
Right now I am going to keep the leases at 1 hour and see if I run into issues with THAT.
Anyway, having seen all the posts about this over the years, I thought I would offer this up. Do I guarantee it will work for your problem? No. But, if you are reading this far... you have tried other things and they have not worked.
As I was explaining the issue to the tech and presenting him my data points, I came to one data point. My iPhone. The NH was showing it as having a valid IP... but the phone was showing no connection AND a self-assigned.
The "self-assigned" bit in there is enigmatic – what was self assigned? – but any mention of an iPhone prompts this:
