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Re: [Xen-users] Wired Network Bridging

Ray Joseph <ray3960852@xxxxxxxxx> wrote:

> 1)  The POSTROUTING command gets the dom0 wireless interface name wlan0 and 
> the $MAC_OF_BRIDGE which is the same as the MAC of the dom0 wireless MAC?

This changes the source MAC address in each outgoing packet to be that of the 
host interface (wlan0 in this case). This is to deal with wireless APs that 
filter packets with a different MAC to the one that initially made the wireless 
connection. As I said, you might try without these ebtables rules - I've found 
some APs are not so fussy, and if that's the case then your life will be so 
much simpler.

> 2)  The PREROUTING commands reference the dom0 wireless interface name and 
> the domU IP address and MAC?

Yes. These two reverse the mangling done by the previous command so that 
packets get to the guests correctly.

> 3)  In domUs, can the interface be defined as an Ethernet?  As such, be given 
> the MAC address of the dom0 wireless interface?  Is there a good way to keep 
> track of what IP addresses the vms are allocated?

They are seen as ethernet interfaces to the guests - the guest does NOT see 
that there is wireless involved. As far as each guest is concerned, they have 
an ethernet interface connected to a switch (the bridge in Dom0) - what's the 
other side of that switch is largely invisible.

No, the guests MUST have unique MAC addresses. Your network will do "very 
interesting things" if you have two devices with the same MAC !

As for IP and MAC allocation and tracking - well there are whole subsections of 
the network management tool industry devoted to that problem ! For small 
networks, just keep a simple text file or spreadsheet (overkill for a handful 
of devices) listing the IP & MAC addresses assigned to each device (real & 

> 4)  In the interfaces file, is there a need to assure the ordering of these 
> two lines:
> pre-up iwconfig wlan0 essid [myessid]                    # 1
> pre-up iw dev wlan0 set 4addr on                            # 2

No idea - as I said, I'm not familiar with wireless networking in these sorts 
of situations (all my Linux systems are either hardwired with ethernet, or VMs 
with no visibility of what's upstream).
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