How do you avoid running out of IP addresses?

[timmy2]

Since most smartphones will remember the wi-fi passkey for an SSID and therefore connect automatically, how does one deal with a public place with many repeat visitors, like a mid-size church, where maybe 50 people might want to actually use the wi-fi on a given day but everyone who has ever connected will also auto-connect upon arriving, thereby using up IP addresses?

I realize I can configure the router's DHCP server for a short lease time but that won't prevent previous users from automatically re-connecting when they arrive at the location, regardless of whether they need to use the wi-fi. It seems to me, therefore, that it would be easy to run out of IP addresses.

What's the solution?

 

[stevech]

It's not an issue of running out of local LAN IP addresses, like 192.168.1.x, because you can change the netmask and DHCP server range to use, say, 192.168.x.x giving you 65535 LAN IP addresses.

But that won't work with consumer WiFi - because most WiFi routers and APs support only 32 or 64 or so simultaneously associated clients, per router/AP. So when the active client table fills, and a new client requests association, what happens? Hard to say: Some vendor products will just ignore the new request. Others will bump the least active or oldest client association and accept the new one.

This all works differently with managed WiFi systems in the pro world, such as you'd find in a public place.

If you need 30 of 60 active associations, in my opinion, you need a pro to select the right hardware and config/install it.

 

[remixedcat]

The OP is going to need to install a few professional access points to deal with the traffic and have them use different channels. If you want layer 3 roaming you are best off going with a few and having them connected to a WLAN controller with layer 3 roaming for smooth handoff from one AP to the other and having the same SSID for full roaming like hospital wifi does, for example.

What is your budget, OP?

I attatched a quick diagram how usual churches are laid out and how you can pull it off

 

[KGB7]

Consumer grade AP or Wifi routers have a lease time for each IP that can be set manually. You can set it to 1440 min or 10 min. So when you disconnect and come back the next day or few hours later to your local Star Bucks, you get a new IP that is not being used.

You can also manually set as to how many clients can connect to an AP, 1-200.

Having multiple AP's is pointless, as AP gets its IPs from a main router they are connected to. A dedicated/stand alone AP does not assign IP's, its the routers job to do so.

Now if you get multiple WiFi routers, then that number increases with each stand alone wifi routers you have on your network, as each wifi router can have its own subnet.


Now here is the down side of having too many clients connected to single AP. Wifi bandwidth limitations.

If you only want your clients to surf the web and send emails, then single AP will be ok for 30-60 clients. If you want your clients to stream Youtube vidoes, then you need to add more AP's and reduce the number of clients per AP down to 10-20.

If your AP is single band and can only provide 150Mbps, then the number goes down even lower, 5 clients per AP.

It all comes down to Bandwidth an AP can provide, even if you have a Gigabit network and a Gigabit connection from ISP.

 

[remixedcat]

Some APs have thier own DHCP like the Meraki MR series. I have an MR12 and I can have them issue thier own IPs using Meraki DHCP

It all depends on the AP/WLAN controller and how they are configured.

I attached a screen shot of my Meraki MR12's LAN/addressing config

 

[KGB7]

Some APs have thier own DHCP like the Meraki MR series. I have an MR12 and I can have them issue thier own IPs using Meraki DHCP

It all depends on the AP/WLAN controller and how they are configured.

I attached a screen shot of my Meraki MR12's LAN/addressing config

I stand corrected. I havent dealt with every single stand alone AP out there.


Thanks.

 

[remixedcat]

Also a lot of enterprise grade APs prolly have this as well.

 

[timmy2]

Thank very much to all who replied.

Thank you to everyone who replied!

I thought maybe I was overlooking a trick that would prevent devices from reconnecting to the network -- or at least prevent them from being assigned an IP address without some action on the user's part.

It seems wasteful to have to buy an expensive router with DHCP capability beyond 254 addresses just because a bunch of devices that may have connected previously will always reconnect when in the facility.

Likewise, given the limitations of how many connections a typical WAP can handle, one must buy additional WAPs -- all of this to handle connections requested by devices without the users' intervention or need.

 

[stevech]

Any router can DHCP more than 8 bits (255) IP addresses, if the net mask is set properly.

As said above, the issue is not DHCP - it's the number of WiFi ASSOCIATIONS supported by the WiFi router. That has nothing to do with IP addresses.

 

[remixedcat]

This ^ Also you have to factor in the number of TCP connections as well. Some routers choke on people sending too many TCP requests regardless of the number of connected clients. Routers with weak CPUs have issues with this. CPU speed is very important for this.

 

[Mr.BobbyBytes]

Subnet masks in consumer routers

I cannot speak to all consumer grade routers but I do know that if you change the subnet mask in an Asus RT-AC66U you will get a dialog box something to the effect that "the available address pool has changed, would you like me to make the changes". Even after saying yes, you will find under the DHCP tab that the listed available address pool has not changed... nor will it allow you to change it beyond the original 254 scope of available addresses.

Now given that it did accept a subnet mask change, I would assume (I didn't test it) that it would route a valid hard coded address, but would never actually assign one outside the range listed under the DHCP tab.

 

[KGB7]

This ^ Also you have to factor in the number of TCP connections as well. Some routers choke on people sending too many TCP requests regardless of the number of connected clients. Routers with weak CPUs have issues with this. CPU speed is very important for this.

Yes and no.


If you buy a consumer grade router for $200 that has a 1,000mhz cpu and put it side by side with a Business class router that is $1,400 with a 600mhz CPU. The Business class router will outperform every single time.

It all comes down to the coding, firmware and the software difference between each class. If you have or might not have noticed, but consumer grade products have far more firmware updates then Business grade products. Thats because every company spends a lot more time and money on development and testing their Business grade products before they are offered for sale. There is also far less frequent updates on Business grade products.

This is why you wont find consumer grade products at Google, or IBM server farms. Thats because Business grade products work right out of the box and perform ten times better, year after year. Because a companies reputation and constant income comes from Business grade products year after year.

Yet you and i, are on the forums with our cheesy butt, $200 routers, trying to figure out why we cant connect to our AiCloud or Apple Express from 15 feet away. That is the difference between a $200 product and a $1,400 product.


So if you want to set up a WiFi at a Church, then Good Lord will have to open his check book and add a zero or two after a dollar sign. Other wise youll be on this forum and in the confession box on your knees for the next six month.

 

[L&LD]

Consumer products push the boundaries of what can be done in the $xxx dollar space. While business grade products (usually) give you features from 1990 for $xxxx.

Sure, they are stable. But better; they are not. Not when equal dollars are compared to tackle any specific problem.

To make the point: let's say your church example needed someone to connect to Apple Express. The answer: buy a second $200 router that does that without issues (i.e. use/buy consumer routers for a single/main purpose) assuming that your choice fixed the issue; you're still $1K ahead of a single (and a single point of failure) business class system that will probably give you less performance with each new feature added every year that it can't or won't support in the name of stability.

With that $1K saved today; you'll be even further ahead in 3-7 years when you upgrade to what's available then. For the same 2014 cost of that single business class product.


Not saying this is the way to go each time. There are good and valid reasons to use specific business grade products for specific requirements.

In the end the dollars will always do the talking and justify a decision one way or another. And they're never wrong (when properly looked at in the long term sense).

 

[KGB7]

10Gbps switch is a 1990s technology?? Interesting........

 

[L&LD]

Wasn't specifically talking about 10Gbps switches - but either way, I said features, not technology.

 

[KGB7]

Ohhh! You mean the the feature that allows you to over clock a fiber optic firewall? Yeah, those bastards!

 

[L&LD]

Ohhh! You mean the the feature that allows you to over clock a fiber optic firewall? Yeah, those bastards!

Okay, I see you don't want to have a serious conversation.

My point being that there are benefits to both scenarios. It's okay if you don't want to see that possibility.

 

[KGB7]

Okay, I see you don't want to have a serious conversation.

My point being that there are benefits to both scenarios. It's okay if you don't want to see that possibility.

I would love to have a serious conversation with you and I will do so under one condition. Call Facebook and NSA and tell them to start using $200 consumer grade products at all their data centers. Because they are throwing money away, while you and I are not paying enough for so so many awesome features.

Talk to you soon.

 

[remixedcat]

Cisco Meraki will challenge everyone's thoughts of both consumer grade and enterprise grade stuff. They are innovative. No need to learn CLI stuff on Meraki, however you get great hardware and the software on the Meraki units is easy to use and powerful. Something the consumer grade router companies need to take a look at.

Using Meraki stuff has made me realize how... naked consumer grade routers are in terms of features.

 

[stevech]

Cisco Meraki will challenge everyone's thoughts of both consumer grade and enterprise grade stuff. They are innovative. No need to learn CLI stuff on Meraki, however you get great hardware and the software on the Meraki units is easy to use and powerful. Something the consumer grade router companies need to take a look at.

Using Meraki stuff has made me realize how... naked consumer grade routers are in terms of features.

Ever looked at Aruba?
The managed APs have been around in enterprise systems for 15-20 years. AireSpace and Aruba were startups that courted Cisco to be acquired.
Cisco bought Linksys way back for retail/consumer.
Way back, Cisco bought Aironet to address the enterprise. Cisco sold and still sells a heck of a lot of this product line.
Then Cisco bought Airespace (to Aruba's disappointment), to get into managed thin-APs for the enterprise. This line has been moderately popular.
This latest acquisition is for enterprise clound-managed WiFi - moving the controller (as in the Airespace and Aruba products), to a cloud as a fee based (annuity) service. This lets an enterprise not have an IT support cost, less capital outlay, and expense the cloud service.