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I have a problem on Ubuntu 10.04.3 LTS x64 with sysctl net.ipv4.netfilter.ip_conntrack_max . If I run this command on shell, I get back an error:

error: net.ipv4.netfilter.ip_conntrack_max" is an unknown key.

It occurred on 2 of our machines after a reboot. The sysctl value net.ipv4.netfilter.ip_conntrack_count and all other conntrack-entries are also affected.

This is really problematic because we have a very high load / traffic system and I have written a Nagios script which check this value, because we had several problems in the past with this value. On other machines I have set the conntrack_max to 196608 to solve any problems but now I can't set the value on the affected machines. Is there set any default value at the moment?

Has anyone an idea to get back the two values on my systems?


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up vote 3 down vote accepted

You might be missing a module (I think is nf_conntrack) You should check if you have it on other machines and try to load it (modprobe). If it solves your problem, do not forget to add it to /etc/modules, so it will be loaded at next reboot.

Hope it helps.

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Thanks. I have compared 2 servers. One of them works fine and the other one whith the nf_conntrack-problem. – FTV Admin Dec 7 '11 at 12:45
The /etc/modules is identic (only 3 entries "loop, lp, rtc") but when i type "lsmod" in the shell, there are serious differences. On the defective server displayed only 30% of the loaded modules then on the server where is everthing fine. – FTV Admin Dec 7 '11 at 12:52
Ok, i have solved it. With: "modprobe nf_conntrack_ipv4" i have manually added the conntrack module and now everything works fine. But how it can happen that after a reboot so many modules suddenly not loaded? – FTV Admin Dec 7 '11 at 13:02
I can only assume that there was some upgrade (kernel probably) and the modules were not loaded at boot time. I suggest rebooting the server with problems to see if the modules are loaded correctly. – Razvan Stefanescu Dec 7 '11 at 14:59
  1. modprobe ip_conntrack
  2. lsmod |grep conn -- if you see entries it means modules have been loaded correctly
  3. sysctl -w -- to write the changes you made under /etc/sysctl.conf
  4. sysctl -p -- to view the changes and see if it was actually loaded.

That is all you need

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forgot sysctl -w, thx – Aki Jan 14 '14 at 18:24

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