Linux – How to generate netflow data in linux

linuxlinux-networkingmonitoringnetflownetworking

We have a number of Linux servers for which I would like to capture netflow data to be processed by a netflow analyzer. I've been spoiled by the ease in which Mikrotik routers allow netflow data generation, but I haven't managed to find an opensource tool that is able to generate netflow data for multiple interfaces on a Linux system.

I have come across fprobe but it seems quite buggy. Admittedly I haven't spent much time with it yet since I'd also like to evaluate some other possibilities. The other tool I've seen mentioned is nprobe, which appears to be GPL, but is not available as a free download since it is only offered for a fee.

The servers on which I plan to generate netflow data are all Gentoo systems, but this shouldn't really make any difference. At most it means I would have to manually compile a tool from source.

Summary: I'm looking for an opensource netflow generator that will work on Linux and allows capturing flows for multiple interfaces.

Best Answer

You should check IPT-NETFLOW, it seems exactly what you need implemented as a kernel module for IPTABLES. It is actively maintained and used succesfully in some ISP so should be good enough. Documentation could be better though (look into README file).

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Short answer: you can't. Ports below 1024 can be opened only by root. As per comment - well, you can, using CAP_NET_BIND_SERVICE, but that approach, applied to java bin will make any java program to be run with this setting, which is undesirable, if not a security risk.

The long answer: you can redirect connections on port 80 to some other port you can open as normal user.

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EDIT: as per comment question - to delete the above rule:

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Chain PREROUTING (policy ACCEPT)
num  target     prot opt source               destination         
1    REDIRECT   tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:8080 redir ports 8088
2    REDIRECT   tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:80 redir ports 8080

The rule you are interested in is nr. 2, so to delete it:

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Best Answer

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