running out of ip address

jimbobwalton

Looking after a schools network and need to increse dhcp numbers..worried we will run out of ip address ..need a cheap fix..can we change the subnet masks on all equipment to 255.255.254.0 and use 510 addresses i.e 192.168.0.1 to 192.168.1.254 ?
and if yes assume all address can see each other over that subnetmask

snappieT

Sure can. Why not go the whole hog and subnet 255.255.0.0, you'll never run out then. 192.168/16 is reserved as private, so you'll have no issues if you use 255.255.0.0 as your mask.

JonathanAnon

Yeah I'd agree with the above.. use the 255.255.0.0 mask.

jimbobwalton

would there not be an issue with broadcast noise? I have read in a few places that anything over 300 connections may cause issues

JonathanAnon

Depends on how chatty the software you are running, how many users are online at one time, and how many broadcasts they are sending, speed of the switches ...

To avoid broadcasts, you could subnet, i.e. have half the computers on the 192.168.1.0 (mask 255.255.255.0) network and half on the 192.168.2.0 (mask 255.255.255.0) network... and have a routing device between them .. the router will block the broadcasts between networks...

However the servers and other resources will have to be placed on one of the networks, and made accessible to the other... And this may take a bit of setting up.. forwarding DHCP, DNS, other issues... you basically have to manually set up replacements for everything that used to be facilitated by broadcasts...

tbh, if you plan on having approx 500 computers on the network, and given that it is a school (not as much usage generally as a business), I would chance putting them all on the one network.. You can always subnet later if you find that it is an issue..

Antar Bolaeisk

Don't worry, we'll be making the switch to IPv6 soon.

Oh, wait

Capt'n Midnight

http://www.faqs.org/rfcs/rfc1918.html

Private Address Space

The Internet Assigned Numbers Authority (IANA) has reserved the
following three blocks of the IP address space for private internets:

10.0.0.0 - 10.255.255.255 (10/8 prefix)
172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

On the 10. range you are limited to just 16,777,214 hosts though of course you could NAT more off by using Routers with a WAN port on the side with limited addresses and the extra hosts on the LAN side


In theory you could setup 65,534 routers on 192.168 and then off each one of those routers you have 1,048,574 other routers each using the full 172.16 range and on each of those you have 16,777,214 hosts on the full 192.168 range.

so if you can get your hands on 68,717,314,050 routers you could support 1,152,883,983,844,114,424 hosts

Nothingbetter2d

we are doomed.... no more ip4 addresses.... prepare for meltdown in 2012 when ip address wars start... the mayan's were right the earth is doomed.

lol but seriously its not that big a deal anymore... most isp have already started implementing ip6