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Community Member

ip helper

i am a ccna, i am new to cisco, but i iam trying to setup a location witch has windows 2000 server running a dhcp server with two scopes mean two subnets, with about 75 workstation my problem how can i configure the routers to forward the right subnet or the scope to the workstations mean some workstation they will use the first scope and the other , will use the scond scope please help

Community Member

Re: ip helper

Hey myouakim,

What you need to do is forward all the dhcp requests to your dhcp server. To do that you have to be in the interface mode of the interface you want the router to listen for braodcasts to and then apply the "ip helper-address".

For example all your pc's that needs to contact the dhcp server are connected to the interface e0 and suppose your dhcp ip address is, so your configuration would be something like this:

router(config)#interface e0

router(config-int)#ip helper-address

that's all, you can also use ip forward-protocol command if you want to be more specific about other things.

Hope that helps.

-Salman Khan

Community Member

Re: ip helper

thank you, but can i connect the two routers on the same switch and have each router to send the right ip address from each scope to the workstations

Community Member

Re: ip helper

You can control this using MAC addresses....


Community Member

Re: ip helper

With DHCP the DHCP scope will see what we call the GiAddr field in the ip header (actually we use another filed in the header and call it GiAddr). When you use a help address statement we put the incoming interfaces ip subnet in this field and forward it to the DHCP server. This field will specify which subnet the client is coming from. With this info we can correspond the right ip subnet the the correct ip address given out.

Hope this Helps


Paul Aquino


Cisco Systems

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