Re: I never thought of this scenario

Rich <rich@example.invalid> wrote:

Marco Moock <mm+usenet-es@dorfdsl.de> wrote:

On 20.04.2024 um 18:07 Uhr Rich wrote:

DHCP is also not a "transport layer" protocol.  Instead, it uses UDP
for its transport layer (see RFC url above, page 22):
 
    "DHCP uses UDP as its transport protocol."
 
Since UDP is itself routable, DHCP is also routable, because DHCP is
simply a protocol definition for sending particular "messages"
inside of UDP packets.

 
That depends on the addresses being used.  When being used on
non-directed broadcast, link-local unicast or link-local multicast,
UDP can't be routed because the IP layer forbids routing of those
packages.

 
Yes, correct.  However, that is not "DHCP" the protocol itself
specifying such.  That is the IP layer specifying that certian
addresses used in UDP packets are not routed.
 
The reason it impacts DHCP is that the "bootstrap an IP address
configuration" portion of DHCP means that those addresses are all the
client can make use of until after it has been configured with a valid
IP address for the local subnet.

Which, thinking about this just now, ironically, makes Lawrence's
statement correct.

DHCP the protocol is itself is not routable -- because DHCP the
protocol is not a transport layer protocol.  It relies upon UDP for its
transport.

And whether a given DHCP message is routed or not is wholly dependent
upon whether the UDP packet carrying the DHCP message is itself
routable.