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New Member

IP helper Address

I am attempting to configure a secondary IP address on an existing interface of a router, which would be a bootp segment with a helper address. When I attempt renew the IP address on the PC connected to the bootp segment, and view the packets on the network, the router fails to forward the broadcast packets. But when I make the bootp segment the primary network on the interface, the router forwards the broadcast packets.

4 REPLIES
New Member

Re: IP helper Address

for this reason you can use only the primary address from each interface. on secondary addresses it doesn't work. so you must consider this in planning phase.

New Member

Re: IP helper Address

I agree, Even better option is to use sub-interfaces even when using a single wire to keep the networks organized.

Cisco Employee

Re: IP helper Address

In later software, 12.0.T or higher, the router will use the secondary address in the GI Addr only if the router sees no response for the DHCP request using the Primary address in the GI Addr. This feature is called DHCP smart-relay.

The command for that is 'ip dhcp smart-relay'.

New Member

Re: IP helper Address

Hi,

Is this command strictly for routers using DHCP on the router, or will it send the DHCP requests to an external DHCP server?

Thanks in advance

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