Hello Michael:

I wanted to let you know that your issue was addressed as of ISC DHCP 4.3.5 and 4.1-ESV-R14 under a different ticket (our newest maintenance releases are 4.3.6 and 4.1-ESV-R15).  Our next feature release will be 4.4.0, due out Q1 of '18.

We addressed the issue by adding two command line options to dhcrelay:


-iu ifname

Specifies an upstream network interface: an interface from which replies from servers and other relay
agents will be accepted.  Multiple interfaces may be specified by using more  than  one  -iu  option.
This argument is intended to be used in conjunction with one or more -i or -id arguments.

-id ifname

Specifies  a  downstream  network  interface: an interface from which requests from clients and other
relay agents will be accepted.  Multiple interfaces may be specified  by  using  more  than  one  -id
option.  This argument is intended to be used in conjunction with one or more -i or -iu arguments.

While I realize this comes after you have moved on to other solutions, I thought you'd like to know.

Regards,

Thomas Markwalder
ISC Software Engineering