Re: [dhcwg] Regarding dhcpv4 client id

Roy Marples <> Mon, 05 October 2020 07:39 UTC

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To: Venkataratnam Naidu <>,
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From: Roy Marples <>
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Date: Mon, 5 Oct 2020 08:39:35 +0100
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Subject: Re: [dhcwg] Regarding dhcpv4 client id
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On 05/10/2020 06:53, Venkataratnam Naidu wrote:
> Hi Experts,
> I have a question on dhcpv4 client id that client sends in dhcp discover/request 
> msg.
> when the client id is other than hardware address, is that mandatory to encode 
> "type 0" in client-identifier.
> if client doesn't encode type 0, does this work in all dhcp server implementations.

 From RFC 2132 section 9.14

Identifiers SHOULD be treated as opaque objects by DHCP servers.

The problem here is should. Servers *do* try to interpet the client id and some 
reject the DHCP outright if it cannot.
The use of MUST would have been better here, but sadly that ship sailed years ago.

RFC 8415 section 11 does improve this for DHCPv6, but sadly there are still 
servers out there that reject unknown DUID types because the word SHOULD is 
still there.

Short answer - no it's not mandatory as per the RFC's but server implementations 
make it so.