Smart Phones maxing ip addresses

brcisna

Hello All,

This is not really a question per sei. Just wanted to share a finding that I run into last week. I actually wondered when this would start happening as far back as last year.
We are in a k-12 school setting. 1000 students
We have four subnets comprised of:
172.28.8.0/24 = servers and secretaries
172.28.11.0/24 = grade school
172.28.13.0/24 = high school
172.28.15.0/24 = teachers and ip phones

Last week i was imaging 60 netbooks when i was almost done i could not get the next one to get an ip address. Looked in the dhcp leases and low and behold all leases were used up. I have never seen this before. Long story short with all of the Smart Phones, Ipods,Ipads the kids are carrying around these are of course trying to get an ip address all the time if they are merely powered on. I have simply setup all AP's in the school as a static ip in the given subnet they are in. I am guessing over the summer I am going to have to do some reconfiguring and have the AP's provide there own subnet.

It slaves me to see some kindergarten kid with both a Smart Phone and an Ipod in the morning. Several of them I know their folks and they don't have two nickels to rub together but ALL of their kids have Smart Phones. Wonder why they don't have any money?,,,,duh…

Anyways, I am sure this scenario would not effect most users in their given enviornment.
The thing is after thinking about this, is with the kid carrying the Smart Phone it eats an ip address in the grade school area,,then they walk to high school for lunch,whatever,and it has eaten an ip address there as well and visa versa. I have thought of changing ip lease times but cant really see any workarounds for this.

Just something to think about.

Take Care,
Barry

stephenw10

IPV6! ;D

GruensFroeschli

You could lower the DHCP-lease time to something like 5 minutes.
This way you free up the available address space a lot faster.

chpalmer

172.28.15.0/23 ? Should get 512 hosts in that subnet..?? … 172.28.15.1 - 172.28.16.254

Another thing Id do is to statically assign (through DHCP) the netbooks a given address and not include that block on the dhcp server page.

So Netbooks say 172.28.15.10 - 172.28.15.80 through static dhcp leases option

DHCP Range- 172.28.15.81 - 172.28.16.250 or something similar...

Am I skewed in this thinking?? Im gonna try it on my test box later... ;)

stephenw10

@chpalmer:

So Netbooks say 172.28.15.10 - 172.28.15.80 through static dhcp leases option

DHCP Range- 172.28.15.81 - 172.28.16.250 or something similar…

Except that's 70 IPs that you can't use when the netbooks arn't on.
I agree though that you want some way of prioritising dhcp leases. Perhaps a list of high priority MACs that will be given addresses ahead of other random devices. Does something like this exist?

Steve

XIII

subnetmask.info is a useful site, you tell it how many nodes you need and the base network and it will tell you what subnet mask and other stuff you need.