[Dnsmasq-discuss] Problem when WinXP firewall is activated (does not reply to ping)

Raphaël HUCK raphael.huck at efixo.com
Fri Dec 1 17:41:02 GMT 2006


According to 
http://technet2.microsoft.com/WindowsServer/en/library/75cd0e1f-f464-40ea-ac88-2060e6769f331033.mspx?mfr=true

DHCP client computers running Windows 2000 or Windows XP that obtain an 
IP address use a gratuitous ARP request to perform client-based conflict 
detection before completing configuration and use of a server offered IP 
address. If the DHCP client detects a conflict, it will send a DHCP 
decline message (DHCPDECLINE) to the server.

If your network includes legacy DHCP clients (clients running a version 
of Windows earlier than Windows 2000), you can use server-side conflict 
detection provided by the DHCP Server service under specific 
circumstances. For example, this feature might be useful during failure 
recovery when scopes are deleted and recreated.

--Raphael



Rune Kock wrote:
> On 12/1/06, Raphaël HUCK <raphael.huck at efixo.com> wrote:
>> There is a problem when the firewall of Windows XP is activated, as it
>> does not reply to ping, and dnsmasq checks with ping whether an IP
>> address is already attributed before giving it to someone.
>>
>> As Windows XP doesn't reply to ping when its firewall is activated,
>> dnsmasq thinks the address isn't in use, and gives it to someone else.
> 
> Back in July, when I asked about using arping rather than ping, Simon 
> replied:
> 
>> Interestingly DHCP clients do the address-in-use check too, and since
>> the client only needs to check the local network, it does use ARP.
> 
> As I understand it, the client should try an arping before using the
> address it has been given by the server.
> 
> The interesting question is whether WinXP actually implements this
> arping.  If Windows follows the specification on this, there should be
> no point in the server using arping.
> 
> 
> Rune





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