Hi,
On Thu, Aug 6, 2015 at 4:53 PM, Klaus Espenlaub <[email protected]> wrote: > Hi Maarten, > > On 06.08.2015 15:18, Maarten Hoes wrote: > > Hi, > > > Well I finally figured it out. On my ISP's wifi modem/router, there is a > setting called 'DHCP Binding'. This can be used to make sure that a certain > MAC always gets the same IP address assigned through DHCP. (essentially > creating a DHCP scope of 1 single IP and 1 single MAC). > > When I enable this for a bridged host, reaching the default gateway > becomes impossible. I verified the MAC both in the VM settings as in the > guest os, and made sure that they match the 'DHCP Binding' settings on the > modem/router. As soon as I remove the entry from the modem/router and > restart the guest, networking resumes as expected. > > I had this setting enabled for the 'old' VM's, but not for the newly > created ones; which explains the difference in behavior. > > Now what I dont understand is why such a setting should/does break bridged > to wifi networking - especially when at the same time NAT does work as > expected with that setting enabled. > > Taking a deep breath... let's start with the most surprising piece of > information for most people. Bridged to wifi actually isn't deserving the > name "bridging" at all. Bridging happens at the Ethernet level, and with > wifi that's not possible as 99% of the wifi cards out there simply don't > support promisc mode (which VirtualBox uses for sending/receiving packets > with the guest's MAC address). > > What "bridged to wifi" implements is a funky routing scheme, packet > filtering/suppression and some packet content rewriting. It entirely shares > the host's MAC address (and uses the guest's IP address for actually > filtering the traffic it needs to receive, so the host's IP stack must not > see the packets targeted at the guest and vice versa), and convinces the > wifi router's DHCP server to give out a lease for each VM (which I guess is > where your solution exploded) even though the MAC address "on the wire" is > always the host's. The final step is to translate the host's MAC address to > the guest's and when the packets are passed to/from the VM. > > Klaus > Thank you for taking the time to elaborate/clarify. It's appreciated. I guess what had me fooled is the fact that the bridged guest's MAC/IP combo's show up in the DHCP lease list on the wifi modem/router. Anyway, I guess I now have a bug to close. Thanks again, - Maarten.
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