Pio2pio: Pio2pio moved page IP forwarding to Linux enable packet forwarding

2015-03-06T20:04:51Z

Pio2pio moved page IP forwarding to Linux enable packet forwarding

← Older revision	Revision as of 22:04, 6 March 2015
(No difference)

Pio2pio: /* Using distribution specific init scripts */

2014-02-23T15:28:08Z

Using distribution specific init scripts

← Older revision		Revision as of 17:28, 23 February 2014
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	FORWARD_IPV4=true		FORWARD_IPV4=true
	and again restart the network service.		and again restart the network service.

			[[Category:linux]]

Pio2pio: Created page with "By default Linux distributions will have IP Forwarding disabled. This is normally a good idea, as most peoples will not need IP Forwarding, but if we are setting up a Linux ro..."

2013-08-06T18:17:55Z

Created page with "By default Linux distributions will have IP Forwarding disabled. This is normally a good idea, as most peoples will not need IP Forwarding, but if we are setting up a Linux ro..."

New page

By default Linux distributions will have IP Forwarding disabled. This is normally a good idea, as most peoples will not need IP Forwarding, but if we are setting up a Linux router/gateway or maybe a VPN server (pptp or ipsec) or just a plain dial-in server then we will need to enable forwarding.

====Check if IP Forwarding is enabled====

Using '''sysctl''' query the '''sysctl kernel''' value '''net.ipv4.ip_forward''' to see if forwarding is enabled or not
sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 0
or checking out the value in the '''/proc''' system:
cat /proc/sys/net/ipv4/ip_forward
0
In the both examples IP forwarding is disabled as show the '''value 0'''
====Enable IP Forwarding on the fly====
As with any sysctl kernel parameters we can change the value of '''net.ipv4.ip_forward''' on the fly without rebooting the system
sysctl -w net.ipv4.ip_forward=1
or
echo 1 > /proc/sys/net/ipv4/ip_forward
the setting is changed instantly; the result will not be preserved after rebooting the system.
====Permanent setting using /etc/sysctl.conf====
To make this configuration permanent is using the file '''/etc/sysctl.conf''' where we add a line containing '''net.ipv4.ip_forward = 1'''
/etc/sysctl.conf:
net.ipv4.ip_forward = 1
if you already have an entry net.ipv4.ip_forward with the ''''value 0''' you can change that to '''1'''.

To enable the changes made in '''sysctl.conf''' you will need to run the command:
sysctl -p /etc/sysctl.conf
On '''RedHat''' based systems this is also enabled when restarting the network service:
service network restart
and on '''Debian/Ubuntu''' systems this can be also done restarting the procps service:
/etc/init.d/procps.sh restart
====Using distribution specific init scripts====
Although the methods presented above should work just fine and you would not need any other method of doing this, I just wanted to note that there are also other methods to enable IP Forwarding specific to some Linux distributions. For example '''Debian''' based distributions might use the setting:
/etc/network/options:
ip_forward=no
set it to '''yes''' and restart the network service. Also '''RedHat''' distributions might set this using:
/etc/sysconfig/network:
FORWARD_IPV4=true
and again restart the network service.

Linux enable packet forwarding - Revision history

Pio2pio: Pio2pio moved page IP forwarding to Linux enable packet forwarding

Pio2pio: /* Using distribution specific init scripts */

Pio2pio: Created page with "By default Linux distributions will have IP Forwarding disabled. This is normally a good idea, as most peoples will not need IP Forwarding, but if we are setting up a Linux ro..."