Implementing VLANs onto our network

[Harry_Greatorex]

Hey Guys,

 

We are in the process of overhauling our Wifi network. In order to accommodate all the new Unifi APs, we are wanting to create VLANS on our switches with a different subnet for the APs. We use HP switches across the site, with a ProCurve E5406 at the core, and mainly ProCurve 2650s in all the other cabs. How do i set up the VLANS on them, and how do i set up a subnet in DHCP?

 

Our current flat network uses a 172.25.16.0/22 CIDR subnet, would i use this for the VLAN or would i need a whole new subnet? I hope this is clear enough, I have no experience with VLANS or subnetting. Any help is greatly appreciated.

 

Thanks!

 

Regards

Harry

[Davit2005]

Online IP CIDR / VLSM Supernet Calculator

 

Workout how many devices you need on each vlan with room for expansion. From this you can work out the size of each subnet and break up the /22 range appropriately. Start with the biggest subnets first, below is what I have done for my home network.

 

You will need a DHCP scope for each subnet that needs automatic addresses i.e. client PCs. You should find some useful articles on here about DHCP scopes and vLANS

 

 

You may be able to use an excel spreadsheet.

[IrritableTech]

First of all you need to confirm if you can expand your IP range or not. If you connect to an RBC or some other WAN network based service provider you may be bound by their limits.

 

After which you can better understand how you can chop up your range to suitable chunks for your devices.

[Harry_Greatorex]

Thanks Guys. In terms of our existing /22 subnet, we are limited in terms of how many IP addresses we have left. To expand, i just used the CIDR calculator to change it to a /20 subnet, giving us enough IP addresses. Then each 172.25.19.0 -> 172.25.20.0 -> 172.25.21.0 group will be configured as its own VLAN? All we would need to change as our subnet mask across the site from 255.255.252.0 to 255.255.240.0, does that make sense?

[IrritableTech]

Thanks Guys. In terms of our existing /22 subnet, we are limited in terms of how many IP addresses we have left. To expand, i just used the CIDR calculator to change it to a /20 subnet, giving us enough IP addresses. Then each 172.25.19.0 -> 172.25.20.0 -> 172.25.21.0 group will be configured as its own VLAN? All we would need to change as our subnet mask across the site from 255.255.252.0 to 255.255.240.0, does that make sense?

 

Your plan should work.

 

Your 5406 will need to act as router, so setup VLANs here first. Your 5406 will end up being the router address for each subnet. And you'll need to input your edge router as the switches default router to ensure devices can get on the Internet.

 

You'll need to create scopes on your dhcp server for each Vlan that requires this service, and enter your IP helper-address in your switch config on each Vlan as well.

 

I'd advise you not to create any wireless subnets too big. A large subnet can soon cause a lot of broadcast which can hit APs hard.

 

Once you have the above set up, it's then time to tag some devices and check they get IPs in the correct ranges, if all is well you need to think about tagging and untagging ports depending on what device is on the other end. I find re patching switches and keeping them logical is best - colour coded patch leads even better.

[IrritableTech]

Oh and don't forget to change your subnet in Active Directory Sites and Subnets. I've forgotten about that once or twice.

[Harry_Greatorex]

Thanks for the information, I am feeling more comfortable implementing this now! Is there any major do's or don'ts that i will need to be aware of? I want to plan this the best i can :-)

 

 

Harry

[Muz]

Do you actually know whether this is a 'spoke' network or not? - i.e connects to main site and has an IP block assigned by them.

 

If it is then you will have to request an ip address space for your new subnet.

 

Main concerns are how your VLANs will be routed between and out of and also how DHCP will work - Relaying.