Re: I never thought of this scenario

On 22/04/2024 09:30, Marc Haber wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

DHCP is similar in that the on;y thing a router has to do is determine
its a UDP broadcast, and if it is, work out where to send it, and what
return address to give it if any..
>
One would expect the router to simply spoof a MAC address on its
interface, and relay responses to that MAC address back to the client
network.
In short its acting like an ethernet switch or bridge
>
I am more curious as to how the DHCP server 'knows' which network
address to give the client, but not interested enough to look it up. :-)

 That's because the DHCP relay agent does not simply "route" the
broadcast packet, it generates a new packet with the client message,
adds information about itself (such as, for example, the IP address of
the Interface where the DHCP broadcast was received on) and forwards
the resulting NEW message as routable unicast to the DHCP server.
 

I.e it does a bit of address translation,  like NAT. It messes with the return address as well as the destination addrress
--
How fortunate for governments that the people they administer don't think.
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