mjhjmtu

I created a Debian VM on VirtualBox with two interfaces: a NAT one (for accessing internet) and a host-only one. However, I do not know how to make both interfaces work at the same time. If I the define the host-only as the adapter 1, I can access my VM from the host but not the internet; if I define the NAT one as adapter 1, I can access the internet but cannot reach my guest Debian.

So, how could I make both interfaces work together?

Note: I am still trying to map some port from my host to the SSH port from my guest SO, so there is no need to suggest me to do it :)

EDIT: This is the output of ifconfig when the first adapter is the host-only one:

eth0 Link encap:Ethernet HWaddr 08:00:27:f6:b2:45 
 inet addr:192.168.56.101 Bcast:192.168.56.255 Mask:255.255.255.0
 inet6 addr: fe80::a00:27ff:fef6:b245/64 Scope:Link
 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
 RX packets:495 errors:0 dropped:0 overruns:0 frame:0
 TX packets:206 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:1000 
 RX bytes:48187 (47.0 KiB) TX bytes:38222 (37.3 KiB)

lo Link encap:Local Loopback 
 inet addr:127.0.0.1 Mask:255.0.0.0
 inet6 addr: ::1/128 Scope:Host
 UP LOOPBACK RUNNING MTU:16436 Metric:1
 RX packets:8 errors:0 dropped:0 overruns:0 frame:0
 TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:0 
 RX bytes:560 (560.0 B) TX bytes:560 (560.0 B)

This is the output of netstat -nr when the first adapter is the host-only one:

Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.56.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0

This is the output of ifconfig when the first adapter is the NAT one:

eth0 Link encap:Ethernet HWaddr 08:00:27:f6:b2:45 
 inet addr:10.0.2.15 Bcast:10.0.2.255 Mask:255.255.255.0
 inet6 addr: fe80::a00:27ff:fef6:b245/64 Scope:Link
 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
 RX packets:53 errors:0 dropped:0 overruns:0 frame:0
 TX packets:59 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:1000 
 RX bytes:6076 (5.9 KiB) TX bytes:5526 (5.3 KiB)

lo Link encap:Local Loopback 
 inet addr:127.0.0.1 Mask:255.0.0.0
 inet6 addr: ::1/128 Scope:Host
 UP LOOPBACK RUNNING MTU:16436 Metric:1
 RX packets:16 errors:0 dropped:0 overruns:0 frame:0
 TX packets:16 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:0 
 RX bytes:1664 (1.6 KiB) TX bytes:1664 (1.6 KiB)

This is the output of netstat -nr when the first adapter is the NAT one:

Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
10.0.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
0.0.0.0 10.0.2.2 0.0.0.0 UG 0 0 0 eth0

The solution was pretty simple: I just had to add the following lines in Debian virtual machine's /etc/network/interfaces file:

allow-hotplug eth1
iface eth1 inet dhcp

The second line instructs the interface to obtain an IP via DHCP. The first line loads the interface at boot time.

To apply the changes to a running system, invoke:

ifup eth1

The name for the eth1 interface may vary, use ifconfig -a to list all available interfaces.

EDIT: full /etc/network/interfaces:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

allow-hotplug eth1
iface eth1 inet dhcp

I was facing similar problem with my Ubuntu 14.04 VM, and Solution suggested by @brandizzi for Debian worked with little change.

EDIT: file /etc/network/interfaces:


# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet dhcp

For UBUNTU 16.04

Run command

ifconfig -a

Look for new interface like in my case it is 'enp0s8'

EDIT file /etc/network/interfaces:

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto enp0s3
iface enp0s3 inet dhcp

auto enp0s8
iface enp0s8 inet dhcp 

Both adapter should be configured in Debian

It seems that in both case you only have one adapter configured, hence your problem.

Create 2 adapters in the VirtualBox configuration of your VM and then start it. If you see only one configured adapter when using ifconfig (a single eth0, no eth1 too), then you should use the network configuration tool for Debian (Network Manager, ifupdown, etc.) to configure both interface in DHCP. So you should have eth0 and eth1 in DHCP.

Ensure you are using separate Private Address space subnets for each interface.

So for example, for the interface that is NAT, you could use an address in 192.168.0.0/16 space.

The interface that is 'host only' could be in the 10.0.0.0/24 space.