Added UPnP content (#1689)

Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

docs/Configuring-Pantheon/Networking/Configuring-Ports.md

@@ -9,6 +9,10 @@ Ports must be exposed appropriately to enable communication. An example port con
 
 When running Pantheon from the [Docker image](../../Getting-Started/Run-Docker-Image.md), [expose ports](../../Getting-Started/Run-Docker-Image.md#exposing-ports). 
 
+!!! tip 
+    Pantheon supports [UPnP](Using-UPnP.md) for home or small office environments where a wireless router 
+    or modem provides NAT isolation. 
+
 ## P2P Networking 
 
 To enable peer discovery, the P2P UDP port must be open for inbound connections.

docs/Configuring-Pantheon/Networking/Using-UPnP.md

@@ -0,0 +1,32 @@
+description: Configuring UPnP with Pantheon
+<!--- END of page meta data -->
+
+# UPnP
+
+Enable UPnP to quickly allow inbound peer connections without manual router configuration. Use UPnP 
+in home or small office environments where a wireless router or modem provides NAT isolation. 
+
+UPnP automatically detects that a node is running in a UPnP environment and provides port forwarding. 
+
+!!! tip 
+    UPnP support is often disabled by default in networking firmware. If disabled by default, explicitly
+    enable UPnP support. 
+    
+## Enabling UPnP 
+
+Use the [`--nat-method`](../../Reference/Pantheon-CLI-Syntax.md#nat-method) command line option to enable UPnP.
+
+!!! note
+    Enabling UPnP may slow down node startup, especially on networks without a UPnP gateway device.
+
+When UPnP is enabled: 
+
+* [Enode](../Node-Keys.md#enode-url) advertised to other nodes during discovery is the external IP address and port. 
+* External address and port are returned by the [`admin_NodeInfo`](../../Reference/Pantheon-API-Methods.md#admin_nodeinfo)
+  JSON-RPC API method for the `enode` and `listenAddr` properties. 
+  
+While Pantheon is running, UPnP does not support: 
+
+* IP address changes
+* Disabling UPnP. To disable UPnP, restart the node without the [`--nat-method`](../../Reference/Pantheon-CLI-Syntax.md#nat-method)
+option or set to `NONE`. 

docs/Configuring-Pantheon/Node-Keys.md

@@ -43,6 +43,9 @@ Specified by the [`--p2p-host`](../Reference/Pantheon-CLI-Syntax.md#p2p-host) an
 The enode is displayed when starting a Pantheon node and can be obtained using the [`net_enode`](../Reference/Pantheon-API-Methods.md#net_enode) 
 JSON-RPC API method. 
 
+If [UPnP](Networking/Using-UPnP.md) is enabled, the enode advertised to other nodes during discovery is the 
+external IP address and port. 
+
 ## Specifying a Custom Node Private Key File
 
 Use the [`--node-private-key-file`](../Reference/Pantheon-CLI-Syntax.md#node-private-key-file) option to specify a custom `key` file in any location. 

docs/Reference/Pantheon-API-Methods.md

@@ -100,6 +100,8 @@ Properties of the node object are:
 
 !!! note
     If the node is running locally, the host of the `enode` and `listenAddr` are displayed as `[::]` in the result. 
+    If [UPnP](../Configuring-Pantheon/Networking/Using-UPnP.md) is enabled, the external address is 
+    displayed for the `enode` and `listenAddr`. 
 
 !!! example
     ```bash tab="curl HTTP request"

docs/Reference/Pantheon-CLI-Syntax.md

@@ -586,6 +586,23 @@ min-gas-price=1337
 The minimum price that a transaction offers for it to be included in a mined block.
 The default is 1000.
 
+### nat-method
+
+```bash tab="Syntax"
+--nat-method=<METHOD>
+```
+
+```bash tab="Command Line"
+--nat-method=upnp
+```
+
+```bash tab="Example Configuration File"
+nat-method="upnp"
+```
+
+Specifies the method for handling [NAT environments](../Configuring-Pantheon/Networking/Using-UPnP.md). 
+Options are `upnp` and `none`. The default is `none` (that is, NAT functionality is disabled).
+
 ### network
 
 ```bash tab="Syntax"

mkdocs.yml

@@ -90,6 +90,7 @@ nav:
       - Bootnodes: Configuring-Pantheon/Networking/Bootnodes.md
       - Configuring Ports: Configuring-Pantheon/Networking/Configuring-Ports.md
       - Managing Peers: Configuring-Pantheon/Networking/Managing-Peers.md
+      - Using UPnP: Configuring-Pantheon/Networking/Using-UPnP.md
     - Consensus Protocols:
       - Pantheon Consensus Protocols: Consensus-Protocols/Overview-Consensus.md
       - Comparing PoA Consensus Protocols: Consensus-Protocols/Comparing-PoA.md