Updates basics_of_linux.md

dnsmasq

```

### Configure Network Interface Cards \(NIC\)

On debian NIC:s are defined and configured in `/etc/network/interfaces`.

    netmask 255.255.255.0

    broadcast 192.168.55.255

    bridge_ports none

```

**Take a interface up and down / start and stop**

It is recommended to take a interface down before configuring it.

### Route

You can configure your routes with the following commands:

Where packets are send in a network depends on the routing of the routing. Every node that  the packet passes in its travel to its destination has a routing table defined, that says where the packet should be directed next. The most simple example is how the traffic of a home network is sent to the router, and then from there forwarded on to somewhere else on the internet. How every host should forward the packets are defined in the linux kernel routing table. You can see the routing table by running this command:

```

ip route

route

ip route

netstat -r

```

Remember that these routes will only be temporary

I think that the most useful of these commands is route, since it includes the column names of the table. Here is an example of the output:

```

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

default         192.168.55.1    0.0.0.0         UG    0      0        0 ens3

192.168.55.0    0.0.0.0         255.255.255.0   U     0      0        0 ens3

```

So let's image that we don't have any routing rules at all. It is completely empty. Like this:

```

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

```

But we have network interface connected, called  eth0. If we now try to ping the router \(the gateway\) on the network, we get this result:

```

~ ping 192.168.55.1

connect: Network is unreachable 

```

At this point we can't even add a route to the gateway. Because the network is unreacheable. So we need to hook outselfs up to the network first.

```

route add -net 192.168.55.0 netmask 255.255.255.0 dev eth0

```

Now our table looks like this:

```

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

192.168.55.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0

```

We still can't ping anything out in the internetz- That's because we are not reaching our gateway \(router\), since we haven't configured it yet.

```

route add default gw 192.168.55.1

```

Remember that these routes will only be temporary.

### Wireless - wpa\_supplicant

Now you should be able to surf the internetz.

### Netstat - Find outgoing and incoming connections

Netstat is a multiplatform tool. So it works on both mac, windows and linux.