Re: I never thought of this scenario

On 4/20/24 14:07, Rich wrote:

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.

Nit-pick:  That's the IP layer saying that certain addresses can't be routed.  It doesn't matter what transport is on top of those IP packets.

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.

Nit-pick:  I believe I've read about DHCP implementations that remember what they used last time and will start to use them instead of 0.0.0.0. If that remembered IP fails / is rejected for some reason then it falls back to a discover.
RFC 951 - Bootstrap Protocol - the precursor to DHCP - section 3 paragraph 2 says:  "In the IP header of a bootrequest, the client fills in its own IP source address if known, otherwise zero.  When the server address is unknown, the IP destination address will be the 'broadcast address' 255.255.255.255."
So I'm not sure that a client /must/ use 0.0.0.0 -> 255.255.255.255 when doing a BOOTP / DHCP request.
--
Grant. . . .