hello!

1st post B)

how many devices should one have on a single subnet before network broadcasts become a problem? 300? 1000? 2000?

we're currently trying to decide on using a single large subnet, or use multiple smaller subnets for our network expansion. i'm rooting for the former solution, since it's much easier to manage in the long run. the issue of broadcasts is the only concern i have.


would upgrading everyone to gigabit or 10 gigabit ethernet help alleviate the problem(if there is one)?


the lan is basically used for the plain vanilla windows file sharing, email, and IRC.

thanks in advance

The rule is that the number of devices you have on a single subnet is limited by how many address are available on that subnet. If you understand subnetting and you have 1000 users you'll have to use a class B private ip address scheme (172.16.0.0).

So in turn if you have only need to supply enough addresses for 1000 users it would go like this.

Network Mask: 172.16.0.0 SM: 255.255.0.0
| ^
Network portion.

Your network would be 172.16.0.0 255.255.248.0
This would give you a total of 30 usable subnets and each subnet providing 2054 usable ip address.

LIke this:

172.16.0.0 | 172.16.0.1 thru 172.16.31.253 | 172.16.31.254
172.16.32.0 | 172.16.32.1 172.16.63.253 | 172.16.63.254
172.16.64.0 | and so on....

You can reconfigure it any way you want. THe nice way about setting a newtork up this way is that you can divide certain subnets and give a subnet base on say "floor of the building" or department or whatever you want.

Using gigabit wouldn't help alleviate broadcast storms. Using switches and routers to do the subnetting is what will help.

thanks for the reply.


actually about 2 years ago, we've added a subnet to augment the old one, but we've managed to run through 252 ip addresses real fast. i'm trying to decide whether the next subnet we'll add should have should have 255 (netmask=255.255.255.0) or 64k hosts(255.255.0.0).

if i were to choose the first option...in the long run, i shudder to think of the resulting network layout. it seems a little too complicated for our setup.

while layer 3 switches would somehow make things easier...i just can't help but wonder if all that complexity is necessary -- i.e. why not just use, say 172.16.x.x/255.255.0.0, which gives you 64k addresses? Given that you use up 1k addresses annually, it should last til 2070!

172.16.0.0 255.255.0.0 would work fine if all of your employees are in one building. You can do it that way and it will work. Subnetting just allows you to have more flexibility with your IP scheme and allows a better way to organize your IP addresses.