Added configurations for main-site linux host and off-site linux host

Added GNS3 example topology image

off-site/scripts/create-bridge

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+#!/bin/sh
+#
+# This script is for creating a bridge interface, assigning an IP address, and adding physical interface ens1 to it.
+
+# Create bridge
+ip link add type bridge
+# name is non deterministic, fix
+ip address add 200.1.0.4/16 dev bridge0
+
+# Change bridge0 mac address to not conflict with bridge interface of other wireguard peer
+ip link set bridge0 address ee:3b:6b:e2:fc:b2
+
+# Add physical nic to bridge
+ip link set ens1 master bridge0
+ip link set ens1 up
+ip link set bridge0 up
+
+# Static Routes
+# default
+ip route add default via 200.1.0.1
+# to reach l2tp tunnel interface through wg0
+ip route add 200.1.0.3/32 via 192.168.1.1
+# to be able to reach wireguard peer over the internet
+ip route add 200.1.0.2/32 via 200.4.0.1

off-site/scripts/create-l2tp

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+#!/bin/sh
+# This script creates an L2TP tunnel and session, then adds the L2TP interface to bridge0
+
+# Create tunnel and session
+ip l2tp add tunnel tunnel_id 123456 peer_tunnel_id 123456 remote 200.1.0.3 local 200.1.0.4 encap ip
+ip l2tp add session tunnel_id 123456 session_id 789 peer_session_id 789
+
+# Change address to not conflict with l2tp interface of other wireguard peer
+ip link set l2tpeth0 address ea:b1:1b:99:1b:a9
+
+# Bridge physical interface with L2TP interface
+ip link set l2tpeth0 master bridge0
+ip link set l2tpeth0 up