The free wifi at my business works for some customers and not others. Help!

I’m writing up a fix to a common tech problem I see at coffee shops, cafes, restaurants, bars and other places that offer free wifi.  Hopefully a few business owners might find this by searching and be able to fix their problems with patrons being unable to connect to their wifi.

A typical consumer wifi router

Many wireless routers look something like this. Some have antennas hidden inside. They either plug into your Internet box (cable modem or DSL modem) or straight into your cable or DSL.

Most businesses offering free wireless internet to customers – small businesses, at least, like a corner bistro, a coffeehouse, or a bookstore – often do so with a consumer router. In other words, the exact same type of device that you might plug into “the internet” (cable modem, DSL, usually) in your home in order to get wireless internet.

Cheap broadband routers are a great thing, but they’re designed for homes and small offices – in other words, places where people don’t come and go very much.  In your home, the same laptops, smartphones, and tablets tend to hang around for hours if not all the time.  Routers are often sold with a pre-made setup for this environment, and some of the settings don’t work well for places where people with many devices come and go a lot, such as a coffee shop or restaurant.

The problem

One of the biggest problems I’ve seen time and again with the free wifi offered by small businesses in my neighborhood is when the router runs out of “DHCP leases.” You can think of a DHCP lease as a ticket that the router hands to any computer, tablet, or smartphone that connects to it. The router says “Here’s this ticket; when you need to talk to a web site, show it to me – oh, and it’s only good for 24 hours. Then you need another ticket.”

The problem is that most consumer routers only have about 100 “tickets” to give out. If the tickets are good for 24 hours, some of the routers won’t hand out any new ones until the oldest ticket expires, meaning some customers can connect until the router runs out of “tickets” (DHCP leases) and then other customers can’t connect. It can be even harder to diagnose because regulars who come in every day will almost always be able to connect with the same device, since they’re still holding a ticket from the previous day!

Symptoms

If this is your problem, you’ll most often see that some customers can use the internet fine, and others can’t use it at all.  Many times customers having problems will be able to connect to your wireless, but then the connection will hang, or keep retrying, or give an error message, and they won’t be able to get onto the internet.  If many customers can get to the internet but it’s acting weird, that can be a couple of different problems that are common with consumer routers, and I’ll write about those in a later post.

Solution

The solution to many wifi connection problems in small businesses is to reduce the length of time the “ticket” lasts. Instead of 24 hours, try 10 minutes. This can cause a few problems of its own, but generally they’ll be much less noticeable than problems caused by long DHCP leases.

I can’t give instructions for every router on the market, but if you go into your router’s settings and find DHCP settings, you’ll see something like “DHCP lease timeout,” “DHCP lease length” etc. This may be measured in seconds or minutes, so here’s a handy-dandy translation table:

  • 1 day = 24 hours = 1440 minutes = 86400 seconds. This is too long a DHCP lease expiration for most neighborhood businesses offering free wifi.
  • 10 minutes = 600 seconds. This often works pretty well, especially where customers don’t stay long and the shop is busy.
  • 30 minutes = 1800 seconds. If customers stay longer, or the store, bar, bakery etc isn’t too large or busy, this will also work okay.

Questions and tips are welcome in the comments!

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