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--- docu:tutos:net:rpi_to_router [2020/02/08 12:58]
admin
+++ docu:tutos:net:rpi_to_router [2020/02/09 22:24] (current)
admin
@@ Line 4: / Line 4: @@
 Today we are going to **convert our raspberry pi** into an effective **router** to create a new local subnet where we can safely host our servers and their services.\\
-The device we are going to use is a **Raspberry Pi 3b model**, but **any device** with *nix, an **ethernet adapter** and 1 free **usb slot** (either 2.0, 3.0, usb c, micro usb) with **usb-to-ethernet support** compiled, should work.\\
+The device we are going to use is a **Raspberry Pi 3b model** with latest Raspbian installed, but **any device** with *nix, an **ethernet adapter** and 1 free **usb slot** (either 2.0, 3.0, usb c, micro usb) with **usb-to-ethernet support** compiled, should work (most systems have this compiled by default, so it should not be a problem). \\
 \\
 === THINGS YOU WILL NEED: ===
 a **small device** (in this case a Pi), a **usb-to-ethernet** cable (to create a new physical address), a **switch** (in case you want to extend your connections), **ethernet cables** (with different sizes, depends on your setup)\\
+=== THINGS YOU COULD NEED: ===
+a **usb hub** just in case your device only has 1 usb slot.
 \\
@@ Line 15: / Line 18: @@
     - **Connect** the your small device to a **working router** (any router with internet access would do the work), connect it using the **onboard ethernet adapter**. In this case the gateway **interface will be eth0**
     - Connect your **usb-to-ethernet** dongle to any free usb slot on your device.
-    - You should see a **new interface**, our subnet **will be on eth1**. If you don't see the new interface  sure your **system supports usb-to-ethernet**)
+    - You should see a **new interface** (`ip addr`), our subnet **will be on eth1**. If you don't see the new interface, make sure your **system supports usb-to-ethernet**)
+    - Connect a **small ethernet cable** from the usb-to-ethernet to a **switch** (for providing networking to other devices)
 <code txt>
@@ Line 22: / Line 26: @@
 Some operations over SSH could make you lose access.
 </code>
+I also recommend you to **remove** network-manager, netplan, or any **networking auto-configuration software**, as our server will be **configured statically** in a way that is **supported by most *nix systems**.\\
+\\
+Start by installing `isc-dhcp-server` package, which is a **dhcp server** so we can automatically **assign ips to our local sub-network** on eth1.
+<code bash>
+apt-get install isc-dhcp-server
+</code>
+\\
+Modify **/etc/default/isc-dhcp-server** to tell isc-dhcp-server to use **your eth1 interface**. You can uncomment the ipv6 line if you need ipv6 on your local network (which usually is not required).
+<code bash>vim /etc/default/isc-dhcp-server</code>
+<file bash isc-dhcp-server>
+# Defaults for isc-dhcp-server (sourced by /etc/init.d/isc-dhcp-server)
+# Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).
+#DHCPDv4_CONF=/etc/dhcp/dhcpd.conf
+#DHCPDv6_CONF=/etc/dhcp/dhcpd6.conf
+# Path to dhcpd's PID file (default: /var/run/dhcpd.pid).
+#DHCPDv4_PID=/var/run/dhcpd.pid
+#DHCPDv6_PID=/var/run/dhcpd6.pid
+# Additional options to start dhcpd with.
+#       Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
+#OPTIONS=""
+# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
+#       Separate multiple interfaces with spaces, e.g. "eth0 eth1".
+INTERFACESv4="eth1"
+#INTERFACESv6="eth1"
+</file>
+We will be using the **192.168.2.0/24 network** for our new subnet, but you can use **anyone you want**!\\
+Modify our dhcpd configuration on **/etc/dhcp/dhcpd.conf**
+<code bash>vim /etc/dhcp/dhcpd.conf</code>
+<file bash dhcpd.conf>
+# time in seconds, setup to your needs
+default-lease-time 600;
+max-lease-time 7200;
+# 192.168.2.0/24
+subnet 192.168.2.0 netmask 255.255.255.0 {
+  authoritative;
+  # the range of ips to give to clients
+  # set at your own needs
+  range 192.168.2.2 192.168.2.254;
+  # i guess this can be omitted
+  option subnet-mask 255.255.255.0;
+  # this is important i guess
+  option broadcast-address 192.168.2.255;
+  # we are going to be 192.168.2.1, the router
+  option routers 192.168.2.1;
+  # you will be the dns server too
+  option domain-name-servers 192.168.2.1;
+  # otherwise, you can simply not configure a dns server and use any other
+  #option domain-name-servers 1.1.1.1;
+}
+# an example of dhcp reservation by mac address
+host adevicename {
+  hardware ethernet 01:23:45:6a:bc:de;
+  fixed-address 192.168.2.130; # .130 is just an example
+}
+</file>
+Set yourself (the router) a **static ip address**:
+<code bash>
+ifconfig eth1 up
+ip addr add 192.168.2.1/24 dev eth1
+</code>
+Configure iptables to **route traffic** from **eth1 to eth0 and viceversa**:
+<code bash>
+# postrouting to our gateway interface eth0
+iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
+# this should in theory, block incoming packets that were not established first
+iptables -A FORWARD -i eth0 -o eth1 -m state --state RELATED,ESTABLISHED -j ACCEPT
+iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT
+# enable ip forwarding if you haven't done yet
+echo 1 > /proc/sys/net/ipv4/ip_forward
+</code>
+To finish the setup, **restart the isc-dhcp-server**
+<code bash>systemctl restart isc-dhcp-server</code>
+\\
+=== Setup a DNS Server (Highly recommended) ===
+We will be using **dnsmasq** as our DNS Server, because it is very easy to install and configure.
+<code bash>apt-get install dnsmasq</code>
+Configure the dns server:
+<code bash>vim /etc/dnsmasq.conf</code>
+<file bash dnsmasq.conf>
+# bind on custom interface or ip
+#except-interface=lo
+#bind-interfaces
+#listen-address=192.168.2.1
+# log dns queries and dhcp requests
+#log-queries
+#log-dhcp
+# expand /etc/hosts hosts to your dns
+expand-hosts
+# forward dns request to this ip
+# when you can't resolve an address
+server=1.1.1.1
+# if omitted, dnsmasq will use resolvconf to return
+# the dns configuration inherited by the dhcp server
+</file>
+Restart the **dnsmasq** server
+<code bash>systemctl restart dnsmasq</code>
+\\
+=== Connect your server or laptop to the switch you've configured earlier, and wollah! ===
+==== Enjoy! ====

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