DHCP: ARP issue, FR2.x vs FR 3.x

Alan DeKok aland at deployingradius.com
Fri Jan 13 11:09:59 CET 2012

Fajar A. Nugraha wrote:
> I'm trying to test a simple DHCP server implementation using FR. The setup:
> - server is using dummy1 interface for dhcp server test purposes, IP
> - client is using virtualbox running on server, with client's eth0
> bridged to server's dummy1, tested using client's "dhclient" command.
> - basic DHCP test using dnsmasq and FR 3 (with freeradius -X) on
> server works fine, so there's no issue about using dummy interface and
> virtualbox.
> Then I test FR 2.2.0 (from v2.1.x git).

  Nope.  You're still using an older version.

  Commit 18f56d3e5e in the v2.1.x branch renamed some of the new DHCP
configuration items, and added documentation describing them.

 The dhcp listen section is
> different, so I adusted it accordingly. But there seems to be a
> problem with arp, and the reply never recached the client (also
> confirmed with tcpdump). Any idea how to make FR2's DHCP work, or at
> least behaves similar to FR3?

  See raddb/sites-available/dhcp.  Look for "src_interface".  It
*should* be using that field to update the ARP table.  If you don't set
it, it *should* use the "interface" field.  When the code updates the
ARP cache, it *should* print an error saying so, and then not send the

  Alan DeKok.

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