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{{AppliesToAXELULite}}
{{AppliesToAXEL ULite TN}}
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|August 2016
|First public release
|-
|{{oldid|5301|1.1.0}}
|August 2016
|Added section about persistent rules
|-
|1.1.1
|August 2016
|Added sysctl persistent settings
|-
|1.1.2
|May 2017
|Fix sysctl parameter
|-
|}
==Introduction==
Thanks to the dual Ethernet interface, SBC Lynx allows to implement non-trivial network configurations. As an example of this flexibility, this article shows how to configure SBC Lynx to implement a Linux-powered router that manages data packet forwarding between two different LANs. This task can be performed in parallel with the other application-specific activities (typically field bus communications, monitoring, control etc.). This solution allows to reduce significantly overall infrastructure costs in many industrial environments where Ethernet networking is popular nowadays.
Before proceeding on port forwarding rules setting, the forwarding capability must be enabled on both <code>eth0</code> and <code>eth1</code> interfaces:
<pre>
root@sbc-lynx:~# sysctl -w net.ipv4.conf.eth0.forwarding=1
net.ipv4.conf.eth0.forwarding = 1
root@sbc-lynx:~# sysctl -w net.ipv4.conf.eth1.forwarding=1
net.ipv4.conf.eth1.forwarding = 1
</pre>
</pre>
===Init ScriptMake <code>iptables</code> configuration persistent===
<code>iptables</code> init script is used to make rules persistent in order to load them automatically on boot.
At the next boot the saved <code>iptables</code> rules will be automatically loaded.
----
Please note that <code>sysctl</code> settings (e.g. the ones used to enable packet forwarding) are not persistent across reboots. To apply sysctl settings at boot time automatically, just add them to [http://linux.die.net/man/5/sysctl.conf <code>/etc/sysctl.conf</code>] as <code>token = value</code>:
<pre>
root@sbc-lynx:~# tail /etc/sysctl.conf
#net.ipv6.conf.all.accept_source_route = 0
#
# Log Martian Packets
#net.ipv4.conf.all.log_martians = 1
#
#kernel.shmmax = 141762560
net.ipv4.conf.eth0.forwarding=1
net.ipv4.conf.eth1.forwarding=1
</pre>
sysctl.conf settings are applied with init script during network configuration (see <code>/etc/init.d/networking</code>)
To check sysctl.conf syntax user can apply those settings also manually with the following command:
<pre>
root@sbc-lynx:~# sysctl -p /etc/sysctl.conf
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.eth0.forwarding = 1
net.ipv4.conf.eth1.forwarding = 1
</pre>
