Subject: [dhcwg] What happens to clients that sends a DHCPDECLINE

From: "Yi Chen" <[email-masked]>
Date: Wed, 23 Aug 2006 17:09:56 -0400

Hi,
 
I wonder if anyone can help me clarify something I read in RFC 2131. According to the RFC:
 
4.3.3 DHCPDECLINE message

   If the server receives a DHCPDECLINE message, the client has
   discovered through some other means that the suggested network
   address is already in use.  The server MUST mark the network address
   as not available and SHOULD notify the local system administrator of
   a possible configuration problem.

However, what the RFC doesn't seem to cover is what happen if the IP being DECLINEd is a static DHCP host. Should the DHCP server keep ignoring the client or give it a dynamic IP from an appropriate range? Since the purpose of a static DHCP host is to make sure that client always gets the same IP, I would think that ignoring the client would be the right approach.But I thought I should ask the people on this list who are much more experienced with DHCP than I do :)
 
Thanks in advance,
 
Yi Chen

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From: Ted Lemon <[email-masked]>
Date: Wed, 23 Aug 2006 14:17:09 -0700

On Aug 23, 2006, at 2:09 PM, Yi Chen wrote:
> However, what the RFC doesn't seem to cover is what happen if the IP  
> being DECLINEd is a static DHCP host. Should the DHCP server keep  
> ignoring the client or give it a dynamic IP from an appropriate  
> range? Since the purpose of a static DHCP host is to make sure that  
> client always gets the same IP, I would think that ignoring the  
> client would be the right approach.But I thought I should ask the  
> people on this list who are much more experienced with DHCP than I  
> do :)

DHCPDECLINE is used by the client to indicate that the IP address that  
was leased is in use by some other device.   So ignoring a DHCPDECLINE  
is a bad idea.   What you should do instead is to notify the  
administrator with some urgency that the IP address is in use.    
Whether to offer the client another IP address, or to ignore it until  
such time as the problem is corrected, is probably something that  
should be configurable by the operator.