osx - How to connect to a Virtualbox guest from the host when network cable unplugged
2014-01
Greg K
I'd like to work offline (I'm flying to the US twice this month), to do this I need access to a linux development server.
Update: After searching for a while, this is the same problem I'm experiencing (except with a Snow Leopard host and Ubuntu 10.04 guest).
When I work from home I boot a VirtualBox VM and that acts as my dev server for the day (providing Apache, PHP & MySQL to run my server side code). However, I'd like to work with my VM when I'm not connected to a network.
I have my Ubuntu VM guest set up with a bridge connection so it can serve HTTP and provide SSH access from inside my local network.
I've tried to manually configure my network settings on both Mac OSX (the host) and Ubuntu (the guest) but I can't even ping my own NIC address (127.0.0.1 can, 192.168.21.x I can't) in OS X when I unplug the cable.
Manual network settings:
$ ifconfig en0
en0: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
ether 00:xx:xx:xx:xx:xx
inet 192.168.21.5 netmask 0xffffff00 broadcast 192.168.21.255
media: autoselect (100baseTX <full-duplex,flow-control>)
status: active
I can ping localhost fine, as well as my VM (.20) and SSH too.
$ ping 192.168.21.5
PING 192.168.21.5 (192.168.21.5): 56 data bytes
64 bytes from 192.168.21.5: icmp_seq=0 ttl=64 time=0.085 ms
64 bytes from 192.168.21.5: icmp_seq=1 ttl=64 time=0.102 ms
64 bytes from 192.168.21.5: icmp_seq=2 ttl=64 time=0.100 ms
64 bytes from 192.168.21.5: icmp_seq=3 ttl=64 time=0.094 ms
$ ping 192.168.21.20
PING 192.168.21.20 (192.168.21.20): 56 data bytes
64 bytes from 192.168.21.20: icmp_seq=0 ttl=64 time=0.910 ms
64 bytes from 192.168.21.20: icmp_seq=1 ttl=64 time=1.181 ms
64 bytes from 192.168.21.20: icmp_seq=2 ttl=64 time=1.159 ms
64 bytes from 192.168.21.20: icmp_seq=3 ttl=64 time=1.320 ms
Network cable unplugged:
$ ifconfig en0
en0: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
ether 00:xx:xx:xx:xx:xx
media: autoselect
status: inactive
$ ping 192.168.21.5
PING 192.168.21.5 (192.168.21.5): 56 data bytes
ping: sendto: No route to host
ping: sendto: No route to host
Request timeout for icmp_seq 0
ping: sendto: No route to host
Request timeout for icmp_seq 1
Does OS X disable the NIC when the network cable is unplugged? Any way to stop it doing this?
coneslayer
Perhaps you can add an additional NIC to the guest, and configure it for Host-only Networking.
Host-only networking is another networking mode that was added with version 2.2 of VirtualBox. It can be thought of as a hybrid between the bridged and internal networking modes: as with bridged networking, the virtual machines can talk to each other and the host as if they were connected through a physical ethernet switch. Similarly, as with internal networking however, a physical networking interface need not be present, and the virtual machines cannot talk to the world outside the host since they are not connected to a physical networking interface.
Tim Alexander
Just a thought but possibly a loopback adaptor might get round this. http://www.stayonline.com/detail.aspx?ID=1215
Greg K
SOLVED: I got this working by reconfiguring the vbox network settings to 192.168.21.19 (in VirtualBox -> Preferences -> Network) and commenting the line specifying a gateway as it's not needed (no external access on the host only interface) as per this post.
I can then SSH to 192.168.21.20 from OSX and connect to Ubuntu. I changed my /etc/fstab mounts to point to //192.168.21.19/
I have a Ubuntu guest configured with two interfaces, eth0 is using NAT and works fine, I can access the net.
The second interface eth1 is set to host only networking and VirtualBox has created a vboxnet0 virtual adapter on the host.
I've configured vboxnet0 in VirtualBox adapter settings with the following:
ip 192.168.21.20
subnet 255.255.255.0
Once the VM guest is running, ifconfig on OSX has vboxnet0 setup as:
vboxnet0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 0a:00:27:00:00:00
inet 192.168.21.20 netmask 0xffffff00 broadcast 192.168.21.255
In the guest, eth0 is set to use DHCP, I've statically assigned eth1 to 192.168.21.20 (this was a mistake and the IPs clash between host and guest):
auto eth1
iface eth1 inet static
address 192.168.21.20 (should be .19)
netmask 255.255.255.0
network 192.168.21.0
broadcast 192.168.21.255
gateway 192.168.21.1
There is no device on 192.168.21.1 - what should I set my gateway to? (turns out a gateway is not needed as it's a HOST only interface). Net access is provided by the NAT adapter.
In the guest the routes look like so:
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.21.0 * 255.255.255.0 U 0 0 0 eth1
10.0.2.0 * 255.255.255.0 U 0 0 0 eth0
default 10.0.2.2 0.0.0.0 UG 100 0 0 eth0
default 192.168.21.1 0.0.0.0 UG 100 0 0 eth1
Route table on OSX:
$ netstat -nr
Routing tables
Internet:
Destination Gateway Flags Refs Use Netif Expire
default 10.77.36.1 UGSc 28 0 en1
10.77.36/22 link#5 UCS 5 0 en1
10.77.39.38 127.0.0.1 UHS 1 2236 lo0
10.77.39.255 link#5 UHLWbI 1 66 en1
127 127.0.0.1 UCS 0 0 lo0
127.0.0.1 127.0.0.1 UH 1 8642 lo0
169.254 link#5 UCS 0 0 en1
192.168.21 link#7 UC 2 0 vboxnet
192.168.21.20 a:0:27:0:0:0 UHLWI 0 4 lo0
192.168.21.255 link#7 UHLWbI 2 64 vboxnet
I can't SSH from the host to the guest (I used to be able to when the VM was configured with a bridged connection):
$ ssh 192.168.21.20
ssh: connect to host 192.168.21.20 port 22: Connection refused
What have I done wrong here? TIA
Greg K
I reconfigured the vboxnet0 virtual adapter IP on the host to 192.168.21.19 so it differs from the guests configuration of .20 - then they don't clash. See my updates in the post with more details about the solution.