add some docs improvments

Signed-off-by: Marek Küthe <m.k@mk16.de>

docs/tunneling/fastd.md

@@ -44,9 +44,9 @@ forward no;
 # Setup a peer to allow incoming connections from or initiate a connection too
 peer "<peerName>"
 {
-    remote <type> "<ip>" port <port>;
+    remote <type> "<hostname>" port <port>;
     key "<peer's public key>";
-    interface "$INTERFACE";
+    interface "%n";
 }
 
 ```
@@ -86,10 +86,10 @@ Now we need to fill in the peer details of the node you are connecting to:
 1. `"<peerName>"`
     * Sets the interface name of the connection with the peer to crxn`<peerName>`
 2. `<type>`
-    * Set this to either `ipv4` or `ipv6` depending of the address being used to connect to the remote peer
-3. `"<ip>"`
+    * Set this to either `ipv4` or `ipv6` depending of the address being used to connect to the remote peer. This parameter is optional and can be omitted.
+3. `"<hostname>"`
     * Set this to the remote peer's fastd address
-4. `"port`
+4. `"<port>`
     * Set this to the remote peer's fastd port
 5. `"<peer's public key>"`
     * Set this to your peer's public key
@@ -99,6 +99,14 @@ Now we need to fill in the peer details of the node you are connecting to:
 
 The last thing to configure now is to rise the interface up when fastd starts (as it normally doesn't rise it for you), all occurences of `<interfaceName>` here should match the one in the `interface <interfaceName>;` declaration as shown earlier.
 
+### Modes
+
+Fastd can provide a tunnel with `multitap` mode on layer 2 or a tunnel with `tun` mode on layer 3. Note that the fatsd has 20 bytes less overhead when using tun.
+
+### A peer is not publicly reachable
+
+
+
 ### Starting and maintaining the daemon
 
 You can then start the daemon as follows: