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From: Marc Haber <mh+usenetspam1118@zugschl.us>
Newsgroups: comp.os.linux.misc
Subject: Re: I never thought of this scenario
Date: Mon, 22 Apr 2024 10:30:04 +0200
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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.

-- 
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Marc Haber         |   " Questions are the         | Mailadresse im Header
Rhein-Neckar, DE   |     Beginning of Wisdom "     | 
Nordisch by Nature | Lt. Worf, TNG "Rightful Heir" | Fon: *49 6224 1600402