DHCP relay IP and gateway IP, possible bad logic?

Alan DeKok aland at deployingradius.com
Mon Mar 4 20:50:30 CET 2013

Igor Smitran wrote:
> As you can see CMTS will relay all requests from CM's and CPE's over
> primary interface address (private_ip/
> radius will get all requests from that IP. all offers need to go back to
> that same ip, no matter what giaddr is sent to client.

  Ah, OK.

  As always:

$ git pull


  I've put some changes in to add a DHCP-Relay-IP-Address.  It's visible
in the reply, and is copied from the original packet giaddr.  The send
logic is:

- if relay-ip-addr, unicast to it
- if giaddr, unicast to it
- if NAK or broadcast flag or no ciaddr, send broadcast
- if yiaddr, unicast to it
- otherwise unicast to ciaddr.

> *i have it already working that way with another dhcp server, in
> production.**
> **also, couple of commercial products that i was testing had exactly the
> same logic implemented, all offers were sent to relay ip, no matter what
> was set as giaddr.*

  OK.  The above changes should fix that.

> I didn't break anything, i have to do it that way.


> As far as dhcp server goes, it would be logical for him to return the
> offer to relay ip. relay will forward it to a client and client will get
> correct data.


> i will try to send debug info tomorrow AM CET...

  Please grab a copy of the v2.x.x branch from git.  It should have all
fixes in it, and it should work.

  Alan DeKok.

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