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Old 09-02-2006, 12:10 PM   #16
Registered: Jul 2006
Location: Maryland, USA
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Originally Posted by theNbomr
(does anyone know whether other nodes also cache the reply, or is it sent uni-cast?)
I appreciate your tutorial, so I took it as a challenge to lookup your only question. My old copy of Network Protocol Handbook has conflicting answers, so I went to the RFC. Here's an excerpt.

Originally Posted by RFC826
Let there exist machines X and Y that are on the same 10Mbit Ethernet cable. They have Ethernet address EA(X) and EA(Y) and DOD Internet addresses IPA(X) and IPA(Y) . Let the Ethernet type of Internet be ET(IP). ...

Machine Y gets this packet, and determines that it understands the hardware type (Ethernet), that it speaks the indicated protocol (Internet) and that the packet is for it ((ar$tpa)=IPA(Y)). It enters (probably replacing any existing entry) the information that <ET(IP), IPA(X)> maps to EA(X). It then notices that it is a request, so it swaps fields, putting EA(Y) in the new sender Ethernet address field (ar$sha), sets the opcode to reply, and sends the packet directly (not broadcast) to EA(X).
So the responses is sent directly back to the requester, not broadcast.
Old 09-11-2007, 10:04 AM   #17
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Here is the best solution, as simple as I can describe it.

-You need to use three different arp -s commands:
arp -s MAC_Address_Of_Box1
arp -s MAC_Address_Of_Box2
arp -s MAC_Address_Of_Box3

-In your script/program everytime you need to access one of the three boxes, you will need to first issue the corresponding arp -s command for the box you are trying to access. For example, say you want to ping to Box2, then ping to Box1, you would have to:

arp -s MAC_Address_Of_Box2
arp -s MAC_Address_Of_Box1

Good luck!
Old 09-12-2007, 01:48 AM   #18
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Registered: Aug 2006
Location: Italy
Distribution: Ubuntu
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Smile Solved

Ok, thank you for your suggestions, and thanks to all.
I'll try asap.
For the moment I managed in modifying the firmware of the three boxes and changing their IPs, after a long "struggle" with the manufacturer...
and now it works!

Thanks again!



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