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smoser/README.md

Created January 25, 2019 18:49
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  1. smoser created this gist Jan 25, 2019.
    45 changes: 45 additions & 0 deletions README.md
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    # nat setup through vpn
    The goal of this excersise was to connect a system to my desktop system and let it share the vpn.

    ## systems
    * **desktop**: It has the following interfaces
    * `wlp3s0`: wireless managed by network manager connected to a wireless network.
    * `tun0`: a vpn device set up and managed by network manager
    * `enp0s25`: an unconnected wireless nic.

    * **laptop**: this system needed wanted to be on the vpn. It has the following interfaces:
    * `eth0`: unconnected wired interface

    ## Setup
    ### Set up "internal" network.
    On desktop set up the ipv4.

    ip link set up dev enp0s25
    ip addr add 192.168.1.1/24 dev enp0s25

    On desktop set up forwarding.

    echo 1 > /proc/sys/net/ipv4/ip_forward
    nic_ex=wlp3s0;
    nic_in=enp0s25
    iptables -t nat -A POSTROUTING -o $nic_ex -j MASQUERADE
    iptables -A FORWARD -i $nic_ex -o $nic_in -m state --state RELATED,ESTABLISHED -j ACCEPT
    iptables -A FORWARD -i $nic_in -o $nic_ex -j ACCEPT

    On desktop run dnsmasq:

    touch /tmp/my.conf
    touch /tmp/my.hosts
    dnsmasq --no-daemon \
    --strict-order --bind-interfaces --except-interface=lo --interface=enp0s25 \
    --listen-address=192.168.1.1 \
    --dhcp-no-override --dhcp-authoritative \
    --dhcp-leasefile=/tmp/my.leases \
    --dhcp-hostsfile=/tmp/my.hosts \
    --dhcp-range=192.168.1.2,192.168.1.254,1h \
    --domain=example.com \
    --conf-file=/tmp/my.conf


    ## Magic
    Now just connect the `eth0` nic of the laptop to the `enp0s25` nic of the desktop and let it dhcp.