DHCPINFORM subnet selection

[Shane Kerr]

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Bruce,

Bruce Hudson wrote:
>     We are seeing new Vista systems broadcast a DHCPINFORM after they get
> their IP address from the DHCP server. When processing this request, the
> DHCP server is using the relay IP address to determine the subnet, rather
> than using the actual IP address of the client. 
> 
>         /* Find the subnet that the client is on. */
>         if (gip.len) {
>             /* XXX - do subnet selection relay agent suboption here */
>             find_subnet(&subnet, gip, MDL);
>         } else {
>             /* XXX - do subnet selection (not relay agent) option here */
>             find_subnet(&subnet, cip, MDL);
>         }
> 
>     In a lot of shared-subnet situations, this is almost certain to give the
> wrong information to the client. 

That's true. In these cases, we really should be using the subnet select relay
agent suboption, right?

>     Does anyone know WHY the relay address is used or if changing the code
> to simply use the client address will cause any other issues?

I think the idea is that the subnet determination should be the same for
DHCPINFORM packets as for DHCPDISCOVER packets.

- --
Shane
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