I want to enable IP masquerading/forwarding on CentOS 7, but when I specify net.ipv4.conf.default.forwarding=1 in /etc/sysctl.conf, it doesn’t work.
Can any one help with this problem?
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×To enable IP forwarding, uncomment this line in /etc/sysctl.conf
$ cat /etc/sysctl.conf | grep ip_forward
#net.ipv4.ip_forward=1
only for centos 6
in my installation of Centos 7:
cat /etc/sysctl.conf
so, you should add into the file
/usr/lib/sysctl.d/50-default.conf
/usr/lib/.... path usually for packages,daemon,services that you install or exist when you installed your os . Relevant config also may exist in /etc/..
/etc/.. path is the place where you as a administrator should be configuring
for ip forwarding you should not be touching any file on /usr/lib/…
same goes for firewalld, systemd for them /etc/firewalld/.. or /etc/systemd/…
you can directly edit the good ol /etc/sysctl.conf or preferably /etc/sysctl.d/99-sysctl.conf
the 99-sysctl.conf is symbolic link to the /etc/sysctl.conf
upon reboot or sysctl -p allows the systemd-sysctl service read the link/nonlink files if they exist if not read sysctl.conf and make necessary entry in /usr/lib/.. and/or load your defined or other variables that there exist and ofcourse giving you ip forwarding for this scenario.
in simple al custom goes in /etc/
you should not be editing /usr/lib/sysctl.d/50-default.conf
you can edit /etc/sysctl.conf
or /etc/sysctl.d/ 99-sysctl.conf
or /etc/sysctl.d/<numberdigits and nameappropriatelyaccordingtoyourpurpose>.conf
t
the last one is user created it dont have to be a linked file. systemd-sysctl will load the values
What?
I google searched and this was the first result. I wanted to add a comment here on my “opinion” of how to implement this.Why?
So when reading the file/etc/sysctl.conf, it seems we have a few options (none are wrong because they all work) listed out. One area not mentioned, which in my opinion, I like more, is where it says:To override # only specific settings, add a file with a lexically later # name in /etc/sysctl.d/ and put new settings there.How?
So after runningsudo -sI then ranecho "net.ipv4.ip_forward = 1" > /etc/sysctl.d/100-sysctl.conf.
Why did I choose to name the file100-sysctl.conf? Because there was a file in there that was99-sysctl.confVerify
You can runsudo sysctl -a | grep ip_forwardor without sudosysctl -a | grep ip_forwardto verify it’s there. I would suggest doing asudo reboot nowand then running thissysctlcommand to verify the setting sticks after reboot.Future State : Started a gist for this that covers ipv6 too : https://gist.github.com/josephdrane/cd6cf46d32c3932c9fb663b4cac105a6
Would love to have contributors on there or stars if you found this useful! Thanks!
Another variant for Centos 6 will work on Centos 7.
/sbin/sysctl -w net.ipv4.ip_forward=1
But temporary.
You should add:
net.ipv4.ip_forward = 1
into file
/usr/lib/sysctl.d/50-default.conf
and
/sbin/sysctl -p
or reboot
it work!