Write page about other interfaces (#162)

* Write page about other interfaces

* Fix typo

Co-Authored-By: MichaelDeciso <42928941+MichaelDeciso@users.noreply.github.com>

source/manual/dhcp.rst

@@ -42,6 +42,8 @@ To set the DHCP settings, go to :menuselection:`Services --> DHCPv4 --> [LAN]`.
 put ``192.168.1.100`` as the start address and ``192.168.1.200`` as the end address. Then click Save. After saving,
 click the “Apply Settings” button.
 
+.. _dhcp-relaying:
+
 -------------
 DHCP relaying
 -------------

source/manual/other-interfaces.rst

@@ -0,0 +1,45 @@
+================
+Other interfaces
+================
+
+Besides wired, wireless and VPN interfaces, there are also some other, virtual interfaces, as well as some
+miscellaneous interface-related. These options can be found under :menuselection:`Interfaces --> Other types`.
+This document briefly explains these options.
+
+------
+Bridge
+------
+
+Bridging allows to create a connection between separate networks, allow traffic on network A destined for network B
+(where both networks are connected to your OPNsense device) to reach it via this bridge. Note that this does not
+include DHCP services—this needs to set using :ref:`DHCP relaying <dhcp-relaying>`.
+
+---
+GIF
+---
+
+GIF (``gif(4)``, Generic Tunnel Interface) can be used to tunnel IPv6 via IPv4 connections. A common use for this are the
+IPv6 tunnel of Hurricane Electric (he.net).
+
+---
+GRE
+---
+
+GRE (``gre(4)``, Generic Routing Encapsulation) is used to create a virtual point-to-point connection, through which
+encapsulated packages can be sent. This can be used to utilise protocols between devices over a connection that
+does not normally support these protocols.
+
+----
+LAGG
+----
+
+LAGG (``lagg(4)``) allows for link aggregation, bonding and fault tolerance. This works best if your network switches
+support. Only unassigned interfaces can be added to LAGG. More information about LAGG can be found in
+`the FreeBSD manual <https://www.freebsd.org/doc/handbook/network-aggregation.html>`_.
+
+----
+VLAN
+----
+
+VLANs (Virtual LANs) can be used to segment a single physical network into multiple virtual networks. This can be
+done for QoS purposes, among other things. For this reason, most ISP-issued IPTV devices utilise VLANs.