adds details for the solo exercise

modules/resources/exercise_networking.md

@@ -264,3 +264,39 @@ I would break it down as such:
 * 4 VM as clients per subnet (so 3 * 4 = 12)
 
 The setup is mirrored on the right side so rinse and repeat.
+
+### Set by step
+
+#### The NAT router
+
+![NAT router](./network_solo_detail1.png)
+
+First focus on the machine that will become your NAT router.
+This part of the exercise is very similar to the static router we made before.
+Looking at the diagram we can see that this machine will need three network interfaces:
+
+* one in bridge mode (so you get an IP from the class DHCP)
+* one in internal network mode for the 10.10.0.0/24 network
+* one in internal network mode for the 172.20.0.0/24 network
+
+The internal network can be a shared one as the networks are separated and we'll set static IP addresses for the two router clients but if it looks cleaner to you, make a named internal network for each of them.
+
+#### The first router
+
+![first router](./network_solo_detail2.png)
+
+Next up is the first router on the left hand side.
+This is also a Debian VM but with four network cards attached!
+All cards will have to be in internal mode where one is connected to the same network as the NAT router's 10.10.0.1 card and the other three will have to be three **new** internally named networks.
+One for each of the ranges because we'll run a DHCP server on this router that will offer different addresses on each interface.
+I advise you to write down which card does which network.
+The IP addresses for the cards on this router have to be set statically because we won't run a DHCP on the 10.10.0.0/24 network.
+
+* 10.10.1.0/24
+* 10.10.2.0/24
+* 10.10.3.0/24
+
+#### The clients
+
+This is easy!
+Create a client, put their network card in the right internal network and they should be good to go!