Running DHCP over PPP interface

[David W. Hankins]

On Fri, Apr 14, 2006 at 10:43:37AM -0400, Dutta, Ashutosh wrote:
> Glenn thanks for your email. The applicability has been discussed in pppext mailing list. It was suggested to use PPP to obtain IP address and use DHCP to obtain the server address (e.g., SIP server etc.). This could be applicable in a CDMA2000 environment.

I think what you want is DHCPINFORM support.

Not presently available in the public release of the server.


I like PPPCP better than DHCP over PPP personally.  Has anyone given any
thought to delivering DHCP option format contents via a new PPPCP in a
general manner (so all DHCP standards action gets to ride inside a single
PPPCP)?


> In my case, I use PPP to obtain an IP address from the PPP server and use DHCP to obtain other server related information. Thus PPP server can act like a relay or DHCP server can always co-exist with the PPP server as well. At this time when we run dhclient -d ppp0, the DISCOVER packet gets garbled and never reaches the PPP server also. 

The default build on most architectures tries to use BPF or similar means
to emit and receive packets...in wire format.  I'm not sure what it will
do to a ppp device.  I suspect it would try to frame like ethernet just
as a default fallback, but it's also possible it would frame as IP, so
no ppp (hdlc wasn't it?) header would be present.

If you do this at all, the right way is DHCPINFORM.  But then you want
to know the dhcp server's ip address.

So if delivering relevant DHCP options via PPPCP is not pallateable to
pppext, I'd suggest at least delivering a 'dhcp server address' option,
which then can be passed to a (not yet released) dhclient which unicasts
a DHCPINFORM to that target server.

-- 
David W. Hankins		"If you don't do it right the first time,
Software Engineer			you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins