Understanding DHCP behavior in case of mobile ip

David W. Hankins dhankins at isc.org
Mon Jun 8 22:13:34 UTC 2009

On Mon, Jun 01, 2009 at 03:18:53PM +0800, LOGANATHAN GOPINATH-XNT436 wrote:
>      We are trying to use the ISC dhcp Server to support mobile ip.  My
> doubt is will the server be able to provide an ip address on a 2 way
> handshake rather than a 4 way handshake . What i mean is instead of a
> discover being sent on behalf of the client ,as the server ip address is
> configured on the Home agent/Foreign agent will the server be able to
> provide an ip address for a DHCP request .

There is no enforced binding between discover and request processing
in the server.  A clent could request a lease out of the blue, and
the server will attempt to provide it, if that is your question, but
will NAK the lease if it cannot supply that client the lease it

There is a 2-message handshake in DHCPv4 known as 'rapid commit'.
which allows a server to ACK a DISCOVER (rather than
OFFER/REQUEST/ACK) if the client supports the feature.  ISC DHCP
supports rapid commit in DHCPv6, but not in DHCPv4.

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
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