Issue with DHCP with Wireless card

Hugh McLenaghan hughmcl at
Thu Mar 13 16:40:10 CET 2014

Now, the source address looks ok, but the destination address is wrong :)

Sending DHCP-Offer of id 81b0fb8a from to

Getting closer :)


> Date: Thu, 13 Mar 2014 10:27:25 -0400
> From: aland at
> To: freeradius-users at
> Subject: Re: Issue with DHCP with Wireless card
> Hugh McLenaghan wrote:
>> When i set this up before I didn't have an IPSEC VPN set up and I got it working.
>> When I came back to work on it, I had set up an IPSEC VPN in the meantime. Now freeradius wasn't working for DHCP, however ISC DHCPD WAS working. So i was assuming it was completely an issue with freeradius. It does have an issue causing the problem, however it has at least identified WHY things are broken for me!
> OK. DHCP gets tricky with multiple interfaces.
>> So i have 2 rules in my ipsec-tools.conf file:-
>> spdadd any -P out ipsec
>> esp/tunnel/yy.yy.yy.yy-xx.xx.xx.xx/require;
>> spdadd any -P in ipsec
>> esp/tunnel/xx.xx.xx.xx-yy.yy.yy.yy/require;
> Hmm... DHCP works via broadcast on the local network, and broadcast
> traffic isn't routed.
>> NOW, what's happening is that the freeradius DHCP server is sending the reply packets FROM to the 10.199.100.x network.
> It's not supposed to do that. The should be sending a reply FROM it's
> own IP address, not However... if it can't discover the
> interfaces IP address, it just uses ISC DHCP has code to troll
> through all of the addresses for an interface, and then uses that.
>> So I guess to fully fix the freeradius DHCP we need to try to get the SRC address of the reply packets coming from the Interface IP and not from
> Done. There's more it can do, but that can wait until after 3.0.2.
>> If I can help in any way, PLEASE let me know.
> This helps enormously. I've pushed a fix. You can either grab the
> "v3.0.x" branch from git && re-build, or you can edit your current
> configuration, and do:
> listen {
> type = dhcp
> ipaddr = *
> src_ipaddr = # add this
> }
> I've also added documentation for the src_ipaddr configuration ite,
>> I'd like to get this resolved, since the features in freeradius are worth it :) Well done on all the features, it's a great product.
> Thanks. We try hard to make FreeRADIUS crush ISC DHCPd. :)
> Alan DeKok.
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