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Community Member

Cant get IP dhcp from Vlan

Hi

I have a router switch twain with vlans configured. From one of my subinterface i have configured ip address dhcp (i also tried ip address dhcp client-id etc), however i can not get ip address. When i configure without vlan and connect the ethernet directly to the router there is no problem. what is the problem?

Thanks in advance.

deniz

2 REPLIES
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Re: Cant get IP dhcp from Vlan

if you've configured the port with a vlan you may also need to configure UDP forwarding so that VLAN has the ability to have hosts request UDP DHCP addresses and these requests get forwarded to the vlan/subnet that the dhcp server resides on.

does your dhcp server reside on a different subnet? if so, configure the SVI with 'ip helper-address x.x.x.x' to have all dhcp requests forwarded properly.

when you connect the ethernet directly to the router, you would not need UDP forwarding for dhcp requests to be forwarded properly; so it makes sense this would work as you've stated.

please see the following link for more UDP forwarding info:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_command_reference_chapter09186a0080087387.html#wp1018606

Community Member

Re: Cant get IP dhcp from Vlan

Thank you, i will try and let you know the result.

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