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ip helper-address question

hi all,

ip helper-address forwards 8 differents broadcast.(ntp,tacacs,bootp,netbeui etc....)

I have bootp clients (terminalX) and dhcp clients (windows pc) on the same subnet.

Is there a way to send bootp request to a remote ip add and dhcp request

to another (remote) ip add ?

If not (as i believe) what would happen if a bootp server receives dhcp request

and if dhcp server receives bootp request ?

Is it a problem or will the dhcp server ignore the bootp request and

bootp server ignore dhcp request?

if i remember well, bootp and dhcp request are based on same dest UDP

port (68) no srce ip add and dest ip add is a broadcast so no way to filter


Community Member

Re: ip helper-address question

We have BOOTP and DHCP with both configured as helper addresses on the LAN interfaces and the one doesn't bother the other.

The BOOTP server doesn't service DHCP requests and the DHCP server doesn't service BOOTP requests.

Re: ip helper-address question

Windows 2000 DHCP servers responds to both Bootp and DHCP requests, so there could be a chance that if you have 2 servers, one separately for each protocol. THe DHCP server will respond to both requests. Again it depends on which type of software, and platform you are using.

Really speaking you dont need to use 2 different servers, one for Bootp and one for DHCP. You can enable both in the same Microsoft win2k server. WIn2k has supp for dynamic Bootp.

If you stil need to run it in different servers, what you can do is configure 2 vlans and put each server in each of them. and in each vlan interface (vlan interface of the clients) , put a helper address to the appropriate vlan subnet directed broadcast. (or unicast would be fine).

Community Member

Re: ip helper-address question

thanks for your post

My pb is that i've got two clients types bootp and dhcp on the same subnet/vlan.

i've got two different servers one for bootp and one for dhcp.

so an ip helper-address will forward both clients request to the same ip address

Is there a way to disable bootp response for a win 2000 dhcp response.

Re: ip helper-address question


Reading more on Microsoft DHCP services, a normal DHCP scope wont respond to a Bootp requests. So unless you create a special scope on the same DHCP server, for a Bootp client, (its named as Bootp address pool), a win2k DHCP server wont respond to Bootp requests. So you do not worry about the DHCP server responding to a Bootp request.

Are you facing any issues with the wrong server, responding for the wrong client ??

Community Member

Re: ip helper-address question

thanks for your answer

I'm not facing this kind of pb ,and would not.

I have to replace a nortel accelar 1100 by a cisco 3550,

and closely regarding the accelar conf it appear than this device sends

bootp req to an ip add and dhcp req to an another ,

cisco can't do that in my knowledges

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