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Hojat Taheri
Asked: 2013-06-22 05:49:16 +0800 CST

How to make IP forwarding permanent?

  • 772

I know that I can enable IP forward by echoing 1 to /proc/sys/net/ipv4/ip_forward, but how can I make this permanent?

By the way I want another method rather than start up scripts, is there any?

routing

3 Answers

  1. Best Answer

    Edit /etc/sysctl.conf and search for the following lines:

    # Uncomment the next line to enable packet forwarding for IPv4
#net.ipv4.ip_forward=1

    Uncomment net.ipv4.ip_forward=1:

    # Uncomment the next line to enable packet forwarding for IPv4
net.ipv4.ip_forward=1

    Or in one line command :

    sudo sysctl -w net.ipv4.ip_forward=1
    • 74

  2. Permanent setting using /etc/sysctl.conf

    If we want to make this configuration permanent the best way to do it is using the file /etc/sysctl.conf where we can 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:

    sudo 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:

    sudo /etc/init.d/procps restart

    Source: How to Enable IP Forwarding in Linux

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  3. If you need to enable it in script you can use commands below to enable

    sed -i 's/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/' /etc/sysctl.conf
sysctl -p

    or disable:

    sed -i 's/net.ipv4.ip_forward=1/net.ipv4.ip_forward=0/' /etc/sysctl.conf
sysctl -p
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