User-class and DHCPINFORM

DELFAIRIERE Thomas thomas.delfairiere at
Thu Oct 15 14:16:57 UTC 2009


I've got XP workstations and DHCP servers configured with a user class like this

class "PCs_User_Class_Chrul" {	
    match if (option  user-class = "mycompany");	
    option domain-name "";	

In default network, the default domain-name option is "".

Some workstations with good settings (user class "mycompany" in the paramaters of the network interface) don't have the good domain-name  (they have instead of

I realize a sniff : 
- when a workstation (with the user-class "mycompany") send DHCPREQUEST or DHCPDISCOVER, the dhcp server respond with the good domain-name "".
- when the same workstation send DHCPINFORM, the dhcp server respond with the default domain-name "".

The rfc 2131 (4.3.1) explains that the user-class is  interpreted by dhcp  server when receiving DHCPREQUEST or DHCPDISCOVER. Why the client send DHCPINFORM and DHCP server responds without interpreting the user class?

Is there a way to force the DHCP server to interpret the user class in the DHCPINFORM message?

Thanks for your ansvers

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