Re: DHCP off topic

[Petr Prcek Janda <prcek zavinac netbox bod cz>]

On Sun, Mar 30, 2008 at 11:43:13PM +0200, Tomas Pelka wrote:
> Dobry vecer,
> resim takovy drobny problem, trochu off topic priznavam. S kolegou jsem 
> se preli o nasledujicim problemu.
> Princip cinnosti DHCP je jiste kazdemu znam. Nejprve klientska stanice 
> posila DHCP_DISCOVER a server odpovida zpravou DHCP_OFFER. Soucasti 
> DHCP_OFFER je i tzv. transaction_ID (podle toho server pozna ktera 
> relace kam patri, alespon tak si to vysvetluji). Otazkou je na jakou MAC 
> adresu je DHCP_OFFER odesilan? V RFC 2131 je napsano ze existuji dva 
> pristupy:
>   1)posila na FF:FF:FF... (striktni varianta)
>   2)na MAC klienta, ktery o IP zadal (liberalnejsi varianta).
> Opravte me pokud jsem neco uvedl nepresne.
> 
> Vi nekdo jestli existuji zaznamy a kde je najit o tom ktery OS jakou 
> varinatu pouziva?
> 

Tak jste me zviklal kouknout do toho rfc, jestli jsem blbej ja, nebo
spatne ctete

xid (4) Transaction ID, a random number chosen by the
        client, used by the client and server to
        associate messages and responses
        between a client and a server.

A k vasemu dotazu - imho to vubec nezalezi na libovuli OS 
(nevim, co ten do toho na co kecat), nebo DHCP serveru, ale je dost 
striktne definovano, kdy se to na jakou adresu posila.

   If the 'giaddr' field in a DHCP message from a client is non-zero,
   the server sends any return messages to the 'DHCP server' port on the
   BOOTP relay agent whose address appears in 'giaddr'. If the 'giaddr'
   field is zero and the 'ciaddr' field is nonzero, then the server
   unicasts DHCPOFFER and DHCPACK messages to the address in 'ciaddr'.
   If 'giaddr' is zero and 'ciaddr' is zero, and the broadcast bit is
   set, then the server broadcasts DHCPOFFER and DHCPACK messages to
   0xffffffff. If the broadcast bit is not set and 'giaddr' is zero and
   'ciaddr' is zero, then the server unicasts DHCPOFFER and DHCPACK
   messages to the client's hardware address and 'yiaddr' address.  In
   all cases, when 'giaddr' is zero, the server broadcasts any DHCPNAK
   messages to 0xffffffff.


        S pozdravem 

                                Petr Janda
--
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