Network map

  localnet  +-------------------------------------+  vmnet  +--------------------+
------------|eth0          gateway            eth1|---------|eth0            vm  |
            |192.168.1.44           192.168.56.101|         |192.168.56.102      |
            +-------------------------------------+         +--------------------+

Default gateway

Probably in the host that has to use the gateway – in our case a virtual machine called vm – there isn’t configured any default gateway because it is only connected to a network and only needs to comunicate with other hosts in that network. However if we want to reach hosts in some other networks, we must add a default gateway which in our case will be the server we are configuring right now. So all the outlined steps will happen in the virtual machine vm.

(root@vm)_$: route add default gw 192.168.56.101 dev eth0

If we want to make this change permanent:

/etc/network/interfaces:
------------------------
auto eth0
iface eth0 inet static
    address 192.168.56.102
    network 192.168.56.0
    netmask 255.255.255.0
    gateway 192.168.56.101      <===

Check

From the vm host we must be able to reach:

  • The gateway
(root@vm)_$: ping 192.168.56.101
  • Another host in the vmnet network
(root@vm)_$: ping 192.168.56.103
  • Another host in the localnet network
(root@vm)_$: ping 192.168.1.1

  • Another host in the internet

    We cannot ping www.google.com because we don’t have name resolution, but if we happen to know the IP address for a Google host, we should be able to reach it

(root@vm)_$: ping 173.194.35.147