f3777878   
   From: mark_cruzNOTFORSPAM@hotmail.com   
      
   Thanks, ALbert, for explanations!   
      
   "Albert Manfredi"  wrote in message   
   news:5fab9098-10be-466b-b9ec-a78ba46d6194@s9g2000yqd.googlegroups.com...   
   On Aug 18, 3:06 am, "Mark"  wrote:   
      
   RFC 2131 is where you need to look. It says:   
      
   "DHCP uses UDP as its transport protocol.  DHCP messages from a client   
   to a server are sent to the 'DHCP server' port (67), and DHCP messages   
   from a server to a client are sent to the 'DHCP client' port (68). A   
   server with multiple network address (e.g., a multi-homed host) MAY   
   use any of its network addresses in outgoing DHCP messages."   
      
   Not clear from RFC 2131. Only the UDP destination port IDs are   
   specified, for a server or a client.   
      
   So I checked RFC 951, for BOOTP, which is the daddy of DHCP. Maybe   
   that RFC has some pearls of wisdom.   
      
   Here's RFC 951 on the topic of UDP port IDs:   
      
   "The reason TWO reserved ports are used, is to avoid 'waking up' and   
   scheduling the BOOTP server daemons, when a bootreply must be   
   broadcast to a client.  Since the server and other hosts won't be   
   listening on the 'BOOTP client' port, any such incoming broadcasts   
   will be filtered out at the kernel level.  We could not simply allow   
   the client to pick a 'random' port number for the UDP source port   
   field; since the server reply may be broadcast, a randomly chosen port   
   number could confuse other hosts that happened to be listening on that   
   port."   
      
   So there's your answer. The important thing is for clients to be   
   listening for replies at UDP port 68. The relay agent, when it   
   receives the DHCP response from the server, will relay that response   
   back to the client, probably using a broadcast IP destination address   
   and UDP destination port 68, on the client's VLAN. But there's no   
   reason for a relay agent to pretend it's a client, when forwarding   
   requests to the server.   
      
   Bert   
      
      
   --   
   Mark   
      
   --- SoupGate-Win32 v1.05   
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