To Subnet Or Not??

[CBuxton]

I'm in the planning stages of redoing the network for the school district I work with. The previous network manager setup on building on a 172.16.x.x address, another on 172.17.x.x, etc, etc, with subnet 255.255.0.0. I've got no problems with this setup, and it works, but I am going to be putting in a core layer 3 switch and wondered if it would be better if I just subnetted the 172.16.x.x address using a mask of 255.255.240.0? Any thoughts or recommendations on why or why I shouldn't do this? Thanks.

 

[nexus9]

Dunno if all your PC/client machines use DHCP... you'll have to change/reboot all the PC's when you change the netmask, right? Sounds like a lot of work. What advantage would this new netmask have over the old..?

-Nexus9

 

[CBuxton]

It wouldn't be a problem since 90%+ percent of my users shut their machines down at night, so I'd just delete the DHCP database and make everybody get a new address when they boot up their machines, but you asked the exact question I'm looking for an answer to. What advantages would this ip address setup give me?

 

[Xanathar]

Advantages : No layer 3 core switch needed, no routing needed.
Disadvantages : Broadcasts (WINS servers will help greatly with this) Can also be countered by throwing large links at it to handle the load. IP amount, will you ever outgrow the subnet?

 

[shadow]

layer3 switches are coming down in prices alot. it may very well be even cheaper to go with a layer3 switch rather than just throw larger links between everything. it's also alot more controled and efficient with a layer2 switch.

 

[chibimike]

It depends on how you have it set up now.
Does each building have a layer 2 switch(es) now?
Or do they have hubs?

How much traffic goes over the network?
Is it mainly for email, or do you do file/print sharing as well?

How many machines are there per building?
The current netmask allows 65k machines per subnet.
Your proposed netmask 255.255.240.0 still allow 4k machines per subnet.
Both numbers are way too high.
Usually the number is kept between 64 and 512 depending on traffic density.
Your broadcast domain is every machine in each building.
If you get one machine that flakes out and starts broadcasting like crazy, you can take down everyone.

How much expansion is expected?
Are they running 10Mb or 100Mb?


There are many variables to consider.

mike