Layered Design Model and DHCP

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Mar 5th, 2010
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I'm trying to update my office's LAN. I've got two L2 access switches connected to two L3 distro switches which is connected to my edge router. My question is how to setup DHCP. Currently the router is acting as the DHCP server. Would I setup the ip helper address on my distro switches? I read that you can only configure the ip helper address on L3 interfaces... so would I configure it on the router uplink, or should my interfaces to the access switches be L3 as well? I'm starting to get confused on what should be L3 and how DHCP would be setup.


Any help would be greatly appreciated.

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Jon Marshall Fri, 03/05/2010 - 08:00
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robert.juric wrote:


I'm trying to update my office's LAN. I've got two L2 access switches connected to two L3 distro switches which is connected to my edge router. My question is how to setup DHCP. Currently the router is acting as the DHCP server. Would I setup the ip helper address on my distro switches? I read that you can only configure the ip helper address on L3 interfaces... so would I configure it on the router uplink, or should my interfaces to the access switches be L3 as well? I'm starting to get confused on what should be L3 and how DHCP would be setup.


Any help would be greatly appreciated.


Robert


You need to set the ip helper address under the L3 interfaces for the vlans you have clients on. So if your access switches are L2 and are connected to the distro switches by L2 trunks and the distro switches have L3 SVIs on them for the vlans then you would add the ip helper address under the L3 SVI config on the distro switches eg.


int vlan 10

ip address 192.168.5.1 255.255.255.0

ip helper-address


Jon

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