Configure Dual NIC Routing on Linux: Separate Internal and External Networks
This guide explains how to set up a Linux server with two network cards so that internal traffic uses its own NIC while external traffic uses the other, including default gateway configuration and persistent route commands.
Company needs a server with two NICs to access both external and internal networks. After configuring the internal NIC first, adding the external NIC and its gateway caused the internal address to become unreachable because no default gateway was set, causing internal traffic to be routed through the external gateway.
To fix this, set the external gateway as the default route and add a specific route for the internal network so that traffic to 192.168.0.0/16 uses eth0.
Commands:
route add default gw 119.222.222.1route add -net 192.168.0.0 netmask 255.255.0.0 dev eth0Persist the routes by adding them to /etc/rc.local. To remove the default gateway, use:
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