Help requested with VLAN setup.

[Joost1988]

Dear all,

Recently I've gotten the care over our companies VLAN system.

I'll try to make a short summary on the network setup.

Incoming Internet Line -> Cisco 877 > UNIX Debian4 server ( VLAN / DHCP ) > 3com SuperStack III 3300

Before I get to my question about replacing the 3com Superstack III 3300 with my new Cisco Linksys SRW224P Managed 24p Switch I'll explain why I feel the need for doing it, and what it's purpose is.

We're the IT department for a reasonable big building with several businesses. Those businesses ( our clients ) rent parts of our incoming internet line. This was setup around the year 2000 by a former college. The issue at hand is that we cannot access the 3com SuperStack III 3300 anymore. No one has a clue about the passwords and it has been secured as Ford Knox, even COM1 is so secured that you cannot do anything.

Since I am now responsable for the security and workflow of this situation I find the current situation unacceptable.

ISSUE:

I can't seem to figure out how to configure the Cisco Linksys SRW244P Managed 24p Switch because I do not have the configuration and never worked with VLANs before.

The DHCP server on the Debian4 server also makes the VLANs and they are already configured with a certain subnet.

f.e. VLAN ID:4 = IP 10.0.4.0/199 SUB 255.255.255.0

Is it really as simple as 'creating' VLAN4 on the Linksys switch and have it assigned a port to send the network over? I can't seem to enter any IP adress linked to a VLAN in the configuration on the switch.

Help would be greatly appriciated!

With regards,

Joost Verweij

[Kishore Chennupati]

Hi,

Dont know much about linksys . But i will  try to give you some idea.

I will try to make this very simple to you. You said that your unix server acts a DHCP server right? Now, what it does is to lease out IP addresses to the PC's that plug into your switch

Since you said you have multiple business each business will be part of one vlan

for eg: Vlan 1- Business A

          Vlan 2 - Business B

          Vlan 3- Business C .. and so on

you can have PC's from all of the business on the same switch yet they are seperate from each other. Thats what a VLAN does. It seperates networks.

So if you work for Business A then  simplly plug your PC into one of the ports and then put that port in vlan 1.You cna configure this from the GUI on the linksys. There should be a manual as how you could do it.

Similalry you can configure the other ports for other businesses. There will a place in the configuratino where you need to specify your dhcp server there you mention the IP address of the unix/debian box

Now when you start your PC it will send a bootp message out to the DHCP server with its mac address and the DHCP servier will give it an IP address from the pool of addresses it has in it. The process is not that simple but im  giving you the basics here.

On your PC you need t put the default gateway of the vlan which you can get from your cisco 877. it should have it.

Hope this gives you some idea. Let me know if you need more help

Regards,

Kishore

[Joost1988]

Dear Kishore Chennupati,

First I'd like to thank you for your reply to my issue.

I'm aware of the fact what VLAN does, but the Switch doesn't offer me a spot to fill in DHCP. ( or the DHCP from the Unix box for that matter. )

So that's why I'm having the idea that the unix scripts who define "VLAN1 = IP X.X.X.X" are instantly being picked up by the switch?

Regards,

Joost

[Kishore Chennupati]

hi,

sorry the cisco router should have  "ip helper addresses" created on the sub interfaces. So , dont worry about filling any DHCP details on the switch. Can you paste the cisco 877 config here if its ok with you? you can remove the passwords

"ip-helper" addresses in Cisco world which act as DHCP relay agent.

What these do is to forward the bootp requests to the DHCP server. The DHCP server then does its job of leasing ip addresses from that pool. so all you need on the switch is to just allocate vlans to the ports :-)

HTH,

Kishore