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I need to forward an interface and I wonder why it is disabled by default.

Will there be security issues or side effects when I enable it?

Edward
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Ricardo
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1 Answers1

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ip_forward is only useful on multihomed systems (i.e. more than one network interface) and makes routing of network packets between those interfaces possible. By enabling ip_forward your box essentially becomes a router.

Routing is an optional network function and as such disabled by default.

As for the downside/possible risks: when one of those interfaces is facing a public subnet (WAN/internet or possible hostile LAN), routing makes attacks possible. That's why you need to address those potential security issues with a firewall.

There is an excellent answer at What is kernel ip forwarding? with more information on the subject.

Edward
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