Dhcp and VLANS


  I created 3 VLANs within my network, the computers in the VLANS were configured to take the IPs from my DHCP server which is located on another subnet, everything is working fine and the clients are able to obrain the IP Automatic, all this VLANs are located in a fiber network, also my dhcp server is configured for different scopes for each VLAN, this setup was done 1 year back, now starting from a week back, some of my clients are not able to obtain an IP address Automatically, to solve this I reseve the IP in my DHCP and it works fine, I want to know why i have to reseve the IP so that the client will take the IP, the only change I did is to create a super scope and add all the scopes  within this scope, any help.

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I assume you're using Microsoft 2003 for a DHCP server.  Everything I read in there about Superscopes talk about "multi-netting" - running multiple logical layer 3 networks on a single layer 2 ethernet segment.

You're not doing this.  You have multiple layer 2 ethernet segments with your vlans, and you have one logical layer 3 network per vlan.

Since your problems started when you implemented superscopes - I would recommend backing them out - especially since you don't need it.  We have about 10 vlans with dhcp forwarding to one 2003 DHCP server - works great.  No super scopes.

Paste from help section:

A superscope is an administrative feature of DHCP servers running Windows Server 2003 that you can create and manage through the DHCP console. Using a superscope, you can group multiple scopes as a single administrative entity. With this feature, a DHCP server can:

Support DHCP clients on a single physical network segment (such as a single Ethernet LAN segment) where multiple logical IP networks are used. When more than one logical IP network is used on each physical subnet or network, such configurations are often called MULTINETS.

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You are using ip helpers command on each vlan interface to point to the dhcp server?

If you are using ACL between the vlans are you allowing bootps traffic to the dhcp server vlan?
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