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From: Marco Moock <mm+usenet-es@dorfdsl.de>
Newsgroups: comp.os.linux.misc
Subject: Re: I never thought of this scenario
Date: Sat, 20 Apr 2024 17:21:00 +0200
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On 17.04.2024 um 03:17 Uhr Lawrence D'Oliveiro wrote:

> No, I didn=E2=80=99t miss it at all. It=E2=80=99s listed under =E2=80=9Cd=
esign goals=E2=80=9D, not=20
> actually under how the spec works.
>=20
> By definition such a protocol cannot work across routers, because
> clients don=E2=80=99t know what routers are available until a DHCP server
> tells them.

It can't work across routers without helpers because the client knows
nothing about the network, so the discover message will got to the
non-directed broadcast 255.255.255.255. Traffic to that address is by
design not being routed because that would mean forward it to the
entire world. Another problem is to get the answer back because the src
address is 0.0.0.0 at this stage. That is why the relay agent is needed
and forward all that with src and dst being unicast addresses.

Even with DHCPv6 a helper is needed if the DHCP server resides on
another link (also called broadcast domain).

--=20
kind regards
Marco

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