[ipxe-devel] custom dhcp client_id option

[Maule Mark]

Yea, they use client-identifier a lot, but I don't see that they ever say what the id should be, only that it is unique on the subnet.  Since in the general case a system might want to have independent ipaddr's from the same subnet assigned to dhcp clients running per-port, wouldn't that mean we need in general for the client id to be unique per port (with the ability to override in special case instances)?
On a separate note, is it even required that the client identifier for the purposes of address assignment come from DHCP option 61?  The pxe spec seems to use the ambiguous "DHCP option tags" terminology, implying that maybe it is the dhcp server that should be configurable.
I think in the short term, for my application, I'm going to modify dnsmasq to prefer option 97 as the client id if it is present, and wait for the dust to settle in iPXE.

 
      From: Michael Brown <mcb30 at ipxe.org>
 To: Maule Mark <mark_maule at yahoo.com>; "ipxe-devel at lists.ipxe.org" <ipxe-devel at lists.ipxe.org>; Wissam Shoukair <wissams at mellanox.com> 
 Sent: Tuesday, April 12, 2016 9:42 AM
 Subject: Re: [ipxe-devel] custom dhcp client_id option
   
On 12/04/16 15:29, Maule Mark wrote:
> But wouldn't that cause issues in the general case?  If all of the IB
> ports will then carry the same client_id, then you can only use dhcp to
> assign an ipaddr to one of them (in the general case).

The client hardware address (chaddr) will still be unique.

RFC2132 states that the "client-identifier MUST be unique among the 
client-identifiers used on the subnet to which the client is attached", 
but doesn't seem to state anywhere whether this is unique per client or 
unique per client port.

The PXE spec does mandate that option 61 contains the system UUID.  The 
only reason we didn't previously comply with this was for the sake of 
IPoIB, where the 20-byte MAC address is too large to fit into the DHCP 
chaddr field.  As far as I can tell, this is no longer relevant since 
the switch to eIPoIB.

Michael


   
 

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      From: Michael Brown <mcb30 at ipxe.org>
 To: Maule Mark <mark_maule at yahoo.com>; "ipxe-devel at lists.ipxe.org" <ipxe-devel at lists.ipxe.org>; Wissam Shoukair <wissams at mellanox.com> 
 Sent: Tuesday, April 12, 2016 9:42 AM
 Subject: Re: [ipxe-devel] custom dhcp client_id option
   
On 12/04/16 15:29, Maule Mark wrote:
> But wouldn't that cause issues in the general case?  If all of the IB
> ports will then carry the same client_id, then you can only use dhcp to
> assign an ipaddr to one of them (in the general case).

The client hardware address (chaddr) will still be unique.

RFC2132 states that the "client-identifier MUST be unique among the 
client-identifiers used on the subnet to which the client is attached", 
but doesn't seem to state anywhere whether this is unique per client or 
unique per client port.

The PXE spec does mandate that option 61 contains the system UUID.  The 
only reason we didn't previously comply with this was for the sake of 
IPoIB, where the 20-byte MAC address is too large to fit into the DHCP 
chaddr field.  As far as I can tell, this is no longer relevant since 
the switch to eIPoIB.

Michael


   
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