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Multi Homed server & default gateway settings

Posted: 11. Jun 2013, 18:21
by sternfan
Hi all,

I have a 2008 r2 server with two nics (eth0 & eth1). Both of them have static IPs and both are plugged into a switch. When setting up eth1 I got a warning about multiple default gateways - so I left it blank. The server can reach the internet just fine.

I would now like to use eth1 as the port for virtualbox. But since eth1 has no default gateway, will it be able to get to the internet?

Should each of the nics on the host have the same default gateway regardless of the warning?

Thanks,
Rob

Re: Multi Homed server & default gateway settings

Posted: 11. Jun 2013, 23:48
by noteirak
Tell us what you want as a final result, now how you think it should be done.
If you tell us exactly the final goal, we can advice you on the best VB setup here.

Re: Multi Homed server & default gateway settings

Posted: 12. Jun 2013, 03:45
by BillG
If you plan to use one NIC exclusively for vms, it does not need any network config at all on the host. The IP, netmask and gateway are assigned to the vm. All of the NIC settings except VirtualBox Bridged Networking Driver should be disabled (from networking and sharing centre on the host).

Re: Multi Homed server & default gateway settings

Posted: 13. Jun 2013, 15:16
by sternfan
Thanks for the help - yes, what I wanted was a NIC for just the VMs (in fact, I may want to do more than 1) and was unsure that this NIC could get to the internet since it cannot within the physical host (no default gateway).

Thanks,
Rob

Re: Multi Homed server & default gateway settings

Posted: 14. Jun 2013, 01:43
by BillG
The bridged networking driver works with the device driver in the host OS to ensure the virtual machines have access to the physical NIC. It is really just a filter driver, sorting out which traffic goes where (working at the MAC address level). The actual IP stack is in the OS of the host or guest machine. That is where a default gateway has some meaning.