RE: [dhcwg] questions on RFC 3046 and RFC 3527

> Hello all,
> 
> I have some questions regarding RFC3046 and RFC3527:
> 
> Q1. 
> 
> RFC3046 defines the Relay Agent Information Option. One of 
> the sub option
> for this option is Agent Remote ID Sub-option. A possible 
> value for this
> sub-option can be "the remote IP address of a point-to-point link".

Note the phrasing that a _possible_ value for this sub-option....

> RFC3527 defines another sub-option for Relay Agent 
> Information Option called
> Link selection sub-option. The possible value for this 
> sub-option can be the
> subnet (of the link) of the DHCP client.
> 
> The question is, why the IP address in "Agent Remote ID 
> Sub-option" can't be
> used to identify the subnet of link for the DHCP client? Why 
> there was a
> need for two separate sub-options to convey the same thing?

Because the RemoteID isn't necessarily an IP address?

At least one well-known standard (DOCSIS) sepcifies that the Remote ID is
the MAC address of the cable modem, and not an IP address.

> Q2.
> 
> RFC3046 says:
> 
> "
> 2.2 Server Operation
> 
>    DHCP servers unaware of the Relay Agent Information option will
>    ignore the option upon receive and will not echo it back on
>    responses.  This is the specified server behavior for unknown
>    options.
> "
> RFC3527 says:
> 
> "
>    When the DHCP server is allocating an address and this 
> sub-option is
>    present, then the DHCP server MUST allocate the address on either:
> 
>       o  the subnet specified in the link-selection sub-option, or;
> 
>       o  a subnet on the same link (also known as a network 
> segment) as
>          the subnet specified by the link-selection sub-option.
> "
> 
> The confusion is: RFC3527 seems to mandate the DHCP server to 
> assign IP
> address based on link-selection sub-option when this 
> sub-option is present
> in the received request, but RFC3046 says that the entire Relay Agent
> Information option can be ignored by the DHCP server if it is 
> not supported.
> Could someone clarify this?

Correct.  If the server doesn't support 3046, then it cannot possibly
support 3527.