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Community Member

IOS dhcp and multiple vlans

hi all,

I have a router with multiple vlans that use the ip helper command. However, i need to define one particular vlan (for wireless option 43) for DHCP option 43. In the IOS of the router i can only define a global DHCP service. Here is my question - will the other vlans that request an IP address with they get the IP address defined on the global IOS defination or continue to use the IP helper IP address?


Re: IOS dhcp and multiple vlans

An ip helper forwards the dhcp requests to a dhcp server elsewhere on the network.

Each subnet (=vlan) has a scope there.

Option 43 should be configured only on the scope(s) where you want this option to be added in the response.

Note: You are incorrect in the assumption of certain limitations on the IOS-based dhcp server. You can add multiple dhcp scopes on a router and each scope can have different options.



Community Member

Re: IOS dhcp and multiple vlans

If an ip helper-address is configured on the interface which receives the DHCPDISCOVER packet, the packet will be converted to a unicast packet and sent to your DHCP server configured in the helper address.

If a packet is received on an interface not configured with a helper-address, the router DHCP will process it.

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