Network bridge and MAC address exposure

[Rand Pritelrohm <rand.pritelrohm@gmx.com>]

Hello,

I am not a network specialist and despite a lot of documentation
readings and searchs on the net I haven't get a simple and clear answer
to my question.

Consider this simple schematic:


    | VM | -----> | HOST | -----> | GW | -----> ISP


Lets say the physical interface name on the 'host' is eth0 and the LAN
subnet is 192.168.0.0.

I want to configure the network on the 'host' in order for the VM to
access the Internet.

Thus I consider 2 scenarios to setup the 'host' network.


1. Bridge using routed subnet:

    ip link add dev br0 type bridge
    ip addr add 192.168.222.1/24 dev br0
    ip link set dev br0 up

    ip tuntap add tap0 mode tap
    ip link set dev tap0 up
    ip link set dev tap0 master br0

    #Then I have to enable routing
    echo '1' > /proc/sys/net/ipv4/ip_forward
    iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE


2. Bridge on the same subnet as the LAN:

    ip link add dev br0 type bridge
    ip link set dev br0 up

    ip link set dev eth0 master br0
    ip link set dev eth0 up
    ip addr add 192.168.0.200/24 dev br0
    ip route add default via 192.168.0.1

    ip tuntap add tap0 mode tap
    ip link set dev tap0 up
    ip link set dev tap0 master br0


For both scenarios the VM is then setup with it's own MAC address and
it's IP on the configured subnet of the bridge.


Here is my question:
    For both scenarios, what is the effectively seen MAC address by the
    GW when the VM access the Internet (host or VM MAC address)?

Regards,
Rand.