DHCP client not getting IP address from Time Warner

[Ask Bjørn Hansen]

On Nov 3, 2009, at 8:21, JASSAL Aman wrote:

> Hello,
>
> The logs display something that I find very disturbing.
> In the dhcpdump log, the DHCPDISCOVER message your interface sends an
> erroneous MAC address, there is a "01:" that is added in front of the
> actual MAC address of your interface. What is sent in the discover  
> message
> is "01:00:..." instead of "00:00:...".

Hi Aman,

Yeah - I should have pointed that out.  I tried forcing it to be  
correct with

interface "vr1" {
   send dhcp-client-identifier 00:00:24:c9:23:c1;
}

to no effect.

http://dl.getdropbox.com/u/25895/dhcp/dhcp-freebsd-2.txt

> Then what happens explains itself : the DHCP server will send a  
> DHCPOFFER
> by using the requesting client's MAC address, but since the given MAC
> address is wrong, he broadcasts it (which I don't think is the  
> behaviour
> that is expected in normal cases...).

I thought the broadcasts were misguided responses to me, too, at first  
-- but looking further I think it's just broadcasting when it's giving  
(or not) IPs to other clients.   I've no idea why it does that.

I only included one, but in http://dl.getdropbox.com/u/25895/dhcp/dhcp-osx.txt 
  you can see that on OS X I get the weird replies to  
ff:ff:ff:ff:ff:ff, too.

I also noticed that OS X adds two extra options in the request:

OPTION:  57 (  2) Maximum DHCP message size 1500
OPTION:  51 (  4) IP address leasetime      7776000 (12w6d)

Just to test how can I make dhclient add those, too?

> I think this is also why the client doesn't emit a DHCPREQUEST  
> (which is
> emitted by the client to confirm that it is choosing the proposed  
> settings
> from the server, and implicitly turning down any other offers made by
> other servers).
>
> I'll look into it when I get back home (at work right now). If  
> possible :
> could you try to connect your Time Warner cable with another  
> interface ?
> Or the same one as the one you used under Mac OS X (that way we  
> would see
> if we get the same behaviour, regardless of the network interface  
> chosen)
> ?

The Soekris box only has vr interfaces; the OS X NIC is in my laptop  
so unless I install FreeBSD on there I won't be able to test  
that. :-)   I did actually try one of the other vr interfaces on the  
Soekris box with the same result (they work fine with isc-dhcp running  
on another FreeBSD box).


  - ask