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Re: [dhcwg] Regarding DHCP Discover with Dest Ip as subnet broadcast

Venkataratnam Naidu <ratnameee@gmail.com> Tue, 19 May 2020 14:55 UTC

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From: Venkataratnam Naidu <ratnameee@gmail.com>
Date: Tue, 19 May 2020 20:25:11 +0530
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To: Ted Lemon <mellon@fugue.com>
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Subject: Re: [dhcwg] Regarding DHCP Discover with Dest Ip as subnet broadcast
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Hi Ted Lemon,

Thank you for your valuable feedback.

Regards,
Venkat.

On Mon, May 18, 2020 at 10:16 PM Ted Lemon <mellon@fugue.com> wrote:

> On May 18, 2020, at 12:23 PM, Venkataratnam Naidu <ratnameee@gmail.com>
> wrote:
>
> Thank you for the reply.  Dhcp client using 255.255.255.255 always works.
> But wanted to know the dhcp server behavior when it receives
> Discover/Request with below. And also would like to know any dhcp-client
> implementations using the "subnet broadcast" as destination ip.
>
>
> If you don’t see the behavior called out explicitly in the spec, you
> should not count on there being any standard behavior.  No correctly
> implemented client will use the subnet broadcast address, because this will
> not work in all cases. Some client that isn’t able to use the link-local
> broadcast may use subnet broadcast and hope for the best, but you can
> assume that there will be cases where this definitely will not work. If the
> client tries to do anything other than DHCPINFORM this way, there is a good
> chance that the DHCP server will guess the wrong subnet and give an address
> that won’t work. Or it might work just fine. But using the 255.255.255.255
> broadcast is required for broadcast packets, not optional.
>
> The DHCP server is permitted to unicast its response, and a client with no
> address listening on 0.0.0.0 is expected to handle this correctly.
>
>

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