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I know that systems in network connect together with IP and Mac address ,But insofar as i now all of OSs running on virtual machine use a common network card.I want to know how another systems connect to vm1 or vm2 in a host machine ? Do we have same mac address in ARP for any vm running on a host OS? or we can configure mac manual?(my network type is Bridge and i use VMWare Fusion 2)

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The virtualization software puts the physical network card in "promiscuous" mode so it gets all traffic sent to the host. The software can then pull out the packets for the virtual MAC addresses its VMs are using. When sending packets, the physical card "spoofs" the MAC, using the virtual adapeter's MAC address. Upstream routers and switches cannot tell the different between a connection to a host with VMs, and a connection to a physical bridge that multiplexes multiple physical hosts. See http://en.wikipedia.org/wiki/MAC_address#Usage_in_Hosts

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Virtual adapters work in much the same way as real ones, it's just all done in software. Virtual switches work in much the same way as real ones, it's just all done in software. The software simulates a switch connected to the real network card and simulates network cards connected to the switch. You can treat it exactly like a real physical network set up just like that.

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That means that we can modify a arbitrary mac address and it save in ARP with my ip address? –  Saman Mar 2 '13 at 6:42

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