# This file describes the network interfaces available on your system
  # and how to activate them. For more information, see interfaces(5).
  # source /etc/network/interfaces.d/*
  # The loopback network interface
  auto lo
  iface lo inet loopback

  # The WAN network interface
  auto eno1
  iface eno1 inet static
    # set up ip address to access modem web page on WAN NIC 
    address 192.168.5.2
    netmask 255.255.255.0
    broadcast 192.168.5.255
	
  # Then LAN networks are eno2 eno3 eno4 in bridged mode br1
  # on the 192.168.1.1 subnet
  auto br1
  iface br1 inet static
    bridge_ports eno2 eno3 eno4
    address 192.168.1.1
    network 192.168.1.0
    netmask 255.255.255.0
    broadcast 192.168.1.255
    dns-nameservers 192.168.1.1
    bridge_stp off  # disable Spanning Tree Protocol
    bridge_fd 9  # forwarding delay
    bridge_hello 5
    bridge_maxage 60

The following is a list of some stanza not used and why:

++++

The gateway directive is not required as any traffic to 192.168.1.1 not on subnet /24 will be Netfiltered and if accepted passed to WAN
  # gateway 192.168.1.1
  
auto eno2 and iface eno2 inet manual are not required as iface inet br1 will bring up the components assigned to it.
  # iface eno2 inet manual
  # iface eno3 inet manual
  # iface eno4 inet manual
  
The use of allow-hotplug eth1 is not used as normally these interfaces should be running. The br1 interface will be used for virtual machine access and must be running to allow correct VM startup. During initial boot this will cause delays as attempts are made to find network devices, particularly any not used. These delays are necessary for reliable start-up and operation.
  # allow-hotplug eno2
  # iface eno2 inet manual
    # pre-up ifconfig $IFACE up
    # pre-down ifconfig $IFACE down

Each Ethernet hardware connection has its own defined unique MAC number, no need to define another. If Ethernet bonding were being used there maybe a need to use this stanza.
  #hwaddress ether xx:xx:xx:xx:xx:xx

Network - Netplan Setup

Debian still defaults to the interface style network setup. It can be set up to use netplan. It is very importqant to remember after installing and setting up netplan to disable the interfaces setup. This can be simply done by deleting, renaming, empting or commenting out the interfaces setup file.

Ubuntu now (as of version 14.04) defaults to Predictable Network Interface Names, also see Systemd Docs. I have no problem with this. In any case, you should always check dev names and not assume names, such as “eth0”

To check available interfaces and names use: ip link, or the more verbose ip a.

Netplan references is a good reference for setting up and using Netplan.

The NIC back panel layout:

 IPMI_LAN
 DisplayPort   USB2-1    USB3-1   LAN3(eth2)   LAN4(eth3)
 HDMI          USB2-0    USB3-0   LAN1(eth0)   LAN2(eth1)   VGA

Due to difficulties with the ISP it 2 modems were attempted in bridge mode; a Netgear DM200 and Draytek Vigor130. The premium Vigor 130 was selected for final use.

It is possible to access the modem web page. The modem manual clearly states that the modem address is “http://192.168.5.1” when in bridge mode.

The network must start-up the WAN NIC to allow pppoe modem Ethernet access and also assign a IP address on this NIC for modem web page access. As the modem is using 192.168.5.1 the router would assign the next address, 192.168.5.2.

To access the router modem webpage the router firewall must also be appropriately configured.

The remaining 3 NICs are setup in bridge mode as router LAN ports. When setup in bridge mode the 3 ports effectively act as a switch with any able to access the router LAN on 192.168.1.1 .

See the Netplan configuration below:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

#Using netplan.io, see /etc/netplan

#source /etc/network/interfaces.d/*

# The loopback network interface
#auto lo
#iface lo inet loopback

# The primary network interface
#allow-hotplug eno2
#iface eno2 inet dhcp

# This file is generated from information provided by
# the datasource.  Changes to it will not persist across an instance.
# To disable cloud-init's network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}

network:
    version: 2
    renderer: networkd
    ethernets:
      # eno1 is always reservered for WAN only
      eno2:
        dhcp4: no
        dhcp6: no
        optional: true
      eno3:
        dhcp4: no
        dhcp6: no
        optional: true
      eno4:
        dhcp4: no
        dhcp6: no
        optional: true
    #Setup Bridge Interface
    bridges:
      br0:
        dhcp4: no
        dhcp6: no
        addresses: [192.168.1.6/24]
        interfaces: [eno2, eno3, eno4]
        gateway4: 192.168.1.1
        nameservers:
          addresses: [192.168.1.1]
        parameters:
          stp: off
          forward-delay: 9s
          hello-time: 2s
          max-age: 12s

systemctl disable bind9
systemctl disable isc-dhcp-server
mv /etc/netplan/50-cloud-init.yaml.old /etc/netplan/50-cloud-init.yaml
mv /etc/netplan/network.yaml /etc/netplan/network.yaml.old

systemctl enable bind9
systemctl enable isc-dhcp-server
mv /etc/netplan/50-cloud-init.yaml /etc/netplan/50-cloud-init.yaml.old
mv /etc/netplan/network.yaml.old /etc/netplan/network.yaml