DHCP response to source address not helper address

[Jason Brandt]

We are running a mixed environment of mostly public addresses, with some
private (nat'd) addresses.  We are trying to use one pair of DHCP servers
to service all networks.  The problem we've run into, is that instead of
responding to source address, the DHCP server responds to the giaddr
address in the DHCP packet.  Is there any way to force the server to
respond to source address?  Here's an example of a request packet (1.98 is
the translated source IP, 190.111 is DHCP server):

  TIME: 2013-06-26 16:36:40.498
    IP: x.x.1.98 (0:f:f8:9c:f7:fc) > x.x.190.111 (0:50:56:a2:20:15)
    OP: 1 (BOOTPREQUEST)
 HTYPE: 1 (Ethernet)
  HLEN: 6
  HOPS: 1
   XID: f18b26e0
  SECS: 0
 FLAGS: 0
CIADDR: 0.0.0.0
YIADDR: 0.0.0.0
SIADDR: 0.0.0.0
GIADDR: 192.168.40.4
CHADDR: 60:36:dd:a7:79:e8:00:00:00:00:00:00:00:00:00:00
 SNAME: .
 FNAME: .
OPTION:  53 (  1) DHCP message type         3 (DHCPREQUEST)
OPTION:  61 (  7) Client-identifier         01:60:36:dd:a7:79:e8
OPTION:  50 (  4) Request IP address        192.168.40.158
OPTION:  12 ( 11) Host name                 saipersonal
OPTION:  81 ( 14) Client FQDN               0-0-0 saipersonal
OPTION:  60 (  8) Vendor class identifier   MSFT 5.0
OPTION:  55 ( 13) Parameter Request List      1 (Subnet mask)
                                             15 (Domainname)
                                              3 (Routers)
                                              6 (DNS server)
                                             44 (NetBIOS name server)
                                             46 (NetBIOS node type)
                                             47 (NetBIOS scope)
                                             31 (Perform router discovery)
                                             33 (Static route)
                                            121 (Classless Static Route)
                                            249 (MSFT - Classless route)
                                            252 (MSFT - WinSock Proxy Auto
Detect)
                                             43 (Vendor specific info)


-- 
Jason K. Brandt
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