DHCP client behavior

Hariharasubramanian Ramasubramanian hramasub at in.ibm.com
Thu Mar 9 23:10:55 AEDT 2017

a) Default the Client ID to the MAC addr
b) Provide an interface (rest?) on the BMC  to configure / provision the
Client ID to an arbitrary string (e.g. ibm-obmc -007)

The need to provision the client ID can be based on the IP addr allocation
policy defined on the DHCP *server* in the data center.

One such use case view here:

Hari !

Hariharasubramanian R.
Power Firmware Development
IBM India Systems & Technology Lab, Bangalore, India
Phone:  +91 80 4025 6950

From:	Patrick Williams <patrick at stwcx.xyz>
To:	OpenBMC Maillist <openbmc at lists.ozlabs.org>
Date:	03/09/2017 10:04 AM
Subject:	DHCP client behavior
Sent by:	"openbmc" <openbmc-bounces
            +hramasub=in.ibm.com at lists.ozlabs.org>


I'm looking for feedback from any networking experts.  We had an issue
reported by Witherspoon system manufacturing that our DHCP client was
not sending MAC addresses as part of the DHCP request as legacy systems
did.  I tracked this down to newer behavior in DHCP clients called
'DUID's, which are intended to be system-specific rather than
interface-specific identifiers (MACs would be interface-specific).

There are three options for IPv4 DHCP clients and two for IPv6:
    * MAC address based client IDs (legacy behavior, IPv4 only).
    * System UUID based DUIDs (single ID per system).
    * IPv6 'link-layer' based DUIDs (single ID per interface?)

I'm curious if anyone has a perspective on how data-centers would like
a BMC to act based on the three options for IPv4.  IPv6 we will need to
decide between system or interface based IDs.  (ie. what should be our
default configuration; individual vendors can always change.)

I have created an issue on Github to track the long-term decision and
as a temporary solution I forced IPv4 to MAC.

Original issue is at [1], follow up for this assessment is at [2], "fix"
in Gerrit is at [3].

[1] https://github.com/openbmc/openbmc/issues/1272
[2] https://github.com/openbmc/openbmc/issues/1280
[3] https://gerrit.openbmc-project.xyz/#/c/2933/

Patrick Williams
[attachment "signature.asc" deleted by Hariharasubramanian

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