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New Member

DHCP and VLANs

We have 200 PC configured with dhcp (on a single Win2k server).

Now we want to segment the LAN with different VLAN, to separate different offices (HR, Management, etc).

The doubt is how to obtain different network address from the same dhcp server, that is in its own vlan.

Thanks, Daniele

7 REPLIES
New Member

Re: DHCP and VLANs

you need to configure 'super-scoping' on the server, and place an ip-helper address on each vlan interface, forwarding the DHCP requests to the IP address of the DHCP server.

New Member

Re: DHCP and VLANs

Thank you.

Is there any document/site where I can find information about this features?

New Member

Re: DHCP and VLANs

try here for the ip helper command reference, and config guide:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/index.htm

For the DHCP superscoping you will need to search on Microsoft.com. Its a pretty common setup, so try google for it as well

New Member

Re: DHCP and VLANs

You don't need to set up a superscope... just an additional regular scope with the range that you need. In the new VLAN, use the IP HELPER-ADDRESS command to redirect DHCP requests to your DHCP server. The requests are marked, so that the DHCP server knows which vlan they came from and, thus, which scope to pick the IP from for the DHCP offer.

You would only use superscopes to use multiple IP address ranges to apply to a single physical network segment (VLAN). You might use them when you've run out of addresses in one range and want to use another range of addresses for that same VLAN or if you're migrating from one IP scheme to another. You do NOT use them for multiple VLANs.

http://www.microsoft.com/windows2000/en/server/help/default.asp?url=/windows2000/en/server/help/sag_DHCP_pro_CreateSuperscope.htm

Rich

New Member

Re: DHCP and VLANs

If you are using Cisco Router with enough memory and latest software you can configure the router as a dhcp server to provide IP addressing for the different Vlan you want implemented. If you have more than one router in the network you can provide redundancy across router using HSRP and configuring different VLANs on either routers providing backup for one another. This will be better than depending on one Win2k server.

New Member

Re: DHCP and VLANs

With only 200 clients, redundancy is not all that vital, although it's extremely easy to create a second DHCP server and split the scopes. I think that the ease of management difference between WIN2k and DHCP on a group of routers is big enough to justify the risk of leaving it on WIN2k. It's gotta be easy enough to maintain that you can teach a peon or a manager to do it, otherwise you never get to go on vacation.

New Member

Re: DHCP and VLANs

Thanks to all for your suggestions!

We have solved my doubt!

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