Multiple VLAN setup on network

[Rattler]

Hi Guys,

Whilst I understand Vlans and have placed one on my network, I am not sure of my current problem. I have six areas on a flat network, each area has a 3com 3300 or 4400 switch, what I would like to do is to put each area on to its own VLAN. All the servers are in one area and would remain on the default VLAN, is it simple to have all the VLAN's access the servers and would this senario cut down on broadcast traffic across the network and enhance the speed. The network has a domain controller for DHCP and this would reside in a different area to the main server room, but will also remain on the default VLAN. I hope this makes sense. Thanking you all in advance.

Regards

Rattler

[Geoff]

Yes this will work, however you would also have to subnet each VLAN and provide sensible routing via your default gateway for each subnet.

Unless you have a decent router (or preferably a few), you will just move the problem there.

[spc-rocket]

@Rattler

Yes this is possible and is an ideal way to segment your network. What you need to do is work our how many vlans you will need and then assign each vlan a subnet. Its important to choose the correct subnet range i.e. the number of valid host on each subnet i.e. 192.168.1.x with a mask of class C default will give you 253 host available. .0 for the subnet identification .1 usually for the vlan id (you need to assign the vlan an ip itself as well) and .255 for the broadcast for that subnet.

This decision will be based on how many PCs or devices you have in each section/block. You may want to have a vlan purely for managing the infrastruture devices i.e. swicthes, routers NMS etc, 1 for servers, 1 for printers, admin network if you have a seperate admin and curric network.

At this point its also worth pointing out that you need to think about any future expansion and just setup a vlan for that as well i.e. wireless, VOIP etc.

In order for intervlan routing you need a router (bad choice! unless you have one of those expensive routers) or a layer 3 switch which does routing at ASIC based and is much quicker. Check your core switch to see if it supports layer 3 functionality. The only difference between a layer 3 switch and router is that the router will have more routing capabilities in terms of routing protocols i.e. BGP, IGRP, RIP etc. However since your network will bring in all the vlans at the core it will know the routes to all vlans and hence you will not need to use any routing protcols and this just cust down the complications even futher.

You will find benefits and broadcast reduction. We have got this kinds of scenario setup at our place and it works and its its a lot clearer to view the network and make decision on expansions etc.

PM if you need more info. We use all ciso gear at our place so i can probably provide some advice on the way to go about it, but may not be much helpful in the configs of 3Com.

Ash.

[Andi]

I'm also considering setting this up as quickly as possible. We had a couple of guys from Pervasive in the other day to do a quick wireless survey in our science block and I thought their eyebrows were going to hit the ceiling when I told him we have a flat network and a /12 subnet. I had absolutely no clue that this would ever be a problem on the network.

What I'm thinking of having is VLan for each data cabinet (which generally only contain one switch at the moment), one VLan for servers/switches and printers, one for the wireless, one for CCTV and another for guests and boarders.

We have a Procurve 4108GL as our main backbone, and 2626 or 2650s in most data cabinets. Some are still left with unmanaged switches (2324 and 2124) in the cabs, and obviously they wouldn't be able to be vlan'd off until we replaced the switches, but as this is only in the planning stage at the moment I have a bit of time to think about all this.

Am I likely to need any extra routers? We currently have one DHCP server which services the whole network. The default gateway is set to our watchguard firewall.

This side of sysadmin is all quite new to me, so of course I will be doing my own research, but if somebody could lamenise it for me that would great.

[Grommit]

Sorry for the dumb question..

But why VLAN ?

What is the point of VLANing?

And would VLANing put any restrictions onto the network access ?

[chaz6]

Sorry for the dumb question..

But why VLAN ?

What is the point of VLANing?

And would VLANing put any restrictions onto the network access ?

VLAN's commonly serve two purposes.

The first is to reduce broadcast traffic.

The second is to separate devices by function or area.

In my network there is a VLAN for each floor of each building, then VLANs for servers, facilities (cctv, etc), routing, telephones, virtual servers and wireless networks (staff, students and eduroam visitors). In most places the routing is performed by layer 3 switches (3Com 7700 and 3Com 5500) and there is also a router on a stick at each campus to do the IPv6 routing as our switches are not capable of doing this. If it is of any use I will upload my VLAN plan for all to see.

[andyrite]

Chaz6
If you would upload it. that would be great. Always looking to refine my setup!

[chaz6]

Glad to help! Please find it at the following url:-
<link removed due to copyright infringment at the request of the college>

Green means "in use"
Orange means "reserved"
Yellow means "in use with multiple networks" (not good practice I know, I will consolidate them into one when it is quiet)
Blue means "spans across wan"

[keithu]

You've got a Harley Davidson Block!? Hot Damn! 8)

[chaz6]

Yep - only one in Europe!

http://news.bbc.co.uk/1/hi/england/h...cs/4552549.stm

For the record, we put 3Com 3870 switches in there, but as yet there are no wireless points installed. However it is close enough that you should be able to pick up a signal from the adjacent building :-)