Add Networking/Creating a MACVLAN Sub-Interface.md

Networking/Creating a MACVLAN Sub-Interface.md

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+**Purpose**:
+You may find that you only have one network adapter on a server / VM and need to have multiple virtual networks associated with it.  For example, Home Assistant exists on the `192.168.3.0/24` network but it needs to also access devices on the `192.168.4.0/24` surveillance network.  To facilitate this, we will make a MACVLAN Sub-Interface.  This will make a virtual interface that is parented to the actual physical interface.
+
+!!! info "Assumptions"
+    It is assumed that you are running Rocky Linux (or CentOS / RedHat).
+
+## Create the Temporary Interface
+You will begin with making a new interface, it will have the name `macvlan0`.
+``` sh
+ip link add macvlan0 link eno1 type macvlan mode bridge
+ip addr add 192.168.4.100/24 dev macvlan0
+ip link set macvlan0 up
+```
+
+## Bind a Docker Network to the Sub-Interface
+Now you need to run the following command to allow docker to use this interface for the `surveillance_network`
+``` sh
+docker network create -d macvlan --subnet=192.168.4.0/24 --gateway=192.168.4.1 -o parent=macvlan0 surveillance_network
+```