How to configure source IP in answer to relayed DHCP requests.

[Glenn Satchell]

No but it sets the IP address that the client will reply to.

Alternatively can you add a static route for Network A with the address
of the router as gateway?

regards,
-glenn
>
>Thanks, but it does not work. According to the man page it is used to set the 
IP address used in a DHCP option field.
>It does not change the source address used to send the IP packet.
>
>Any other ideas?
>
>Venlig Hilsen / Regards 
>Morten
>
>-- 
>Morten Laursen, M.Sc.S.E.
>RTX Telecom A/S - http://www.rtx.dk/
>Direct phone: (+45) 96 32 24 03
>
>
>> -----Original Message-----
>> From: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org]On
>> Behalf Of VKR V
>> Sent: 14. december 2006 19:23
>> To: dhcp-users at isc.org
>> Subject: Re: How to configure source IP in answer to relayed DHCP
>> requests.
>> 
>> 
>> server-identifier 
>> <specify_the_IP_you_want_clients_to_identify_DHCP_server>;
>> 
>> 
>> Morten Laursen <MLA at rtx.dk> wrote:  Hi,
>> 
>> As the subject indicates, I have a bit of a complex setup:
>> 
>> network A <-> [router] <-> network B <-> [DHCP server] <-> network C
>> 
>> My DHCP server has 2 interfaces (one connected to the 
>> internet and one private) for which it serves DHCP addresses. 
>> I run dhpcd 3.0.4
>> 
>> From my normal wokring network (not on the sketch) I have 
>> access to both the machine's interfaces, so to get that to to 
>> work I have configured source based routing, so it answers on 
>> network B or C depending on the sender address, i.e. it 
>> answer on the network where it got the reply. That works fine.
>> 
>> My problem is that the devices on network A uses the DHCP 
>> server via DHCP relay in the router. When dhcpd receives the 
>> requests from the router it replies with the IP address 
>> belonging to network C, so the reply is sent to network C and 
>> is never received by the client.
>> 
>> So the question is how can I configure either 
>> a) that dhcpd always uses a specified IP address as source IP 
>> in replies to relayed DHCP requests or even better
>> b) that dhcpd uses the source address where it received the 
>> request for the reply.
>> 
>> (I guess the problem arises because the relayed DHCP requests 
>> from the router uses the routers network A address as source, 
>> so dhcpd cannot from the packet's IP address determine which 
>> interface to use)
>> 
>> 
>> Any ideas would be appreciated.
>> 
>> 
>> Venlig Hilsen / Regards 
>> Morten
>> 
>> -- 
>> Morten Laursen, M.Sc.S.E.
>> RTX Telecom A/S - http://www.rtx.dk/
>> Direct phone: (+45) 96 32 24 03
>> 
>> 
>> 
>> 
>>  
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>