Suricata - multiple interface configuration with af-packet

Suricata is a very flexible and powerful multithreading  IDS/IPS/NSM.

Here is a simple tutorial (tested on Debian/Ubuntu) of how to configure multiple interfaces for af-packet mode with Suricata (af-packet mode works by default/out of the box on kernels 3.2 and above). Lets say you would like to start simple IDSing with Suricata on eth1, eth2 and eth3 on a particular machine/server.


In your suricata.yaml config (usually located in /etc/suricata/) find the af-packet section and do the following:

af-packet:
  - interface: eth2
    threads: 16
    cluster-id: 98
    cluster-type: cluster_cpu
    defrag: no
    use-mmap: yes
    ring-size: 200000
    checksum-checks: kernel
  - interface: eth1
    threads: 2
    cluster-id: 97
    cluster-type: cluster_flow
    defrag: no
    use-mmap: yes
    ring-size: 30000
  - interface: eth3
    threads: 2
    cluster-id: 96
    cluster-type: cluster_flow
    defrag: no
    use-mmap: yes
    ring-size: 20000

Of course feel free to adjust the ring-sizes (packet buffers) as you see fit for your particular set up.
NOTE:  do not forget to use a different cluster-id

so now you can start suricata like so:

suricata -c /etc/suricata/suricata.yaml -v --af-packet 

That above will start Suricata which will listen on eth2 with 16 threads with cluster_type: cluster_cpu and on eth1,eth3 with 2 threads each with cluster_type: cluster_flow. Have a look in your suricata.log file for more info.

If you would like to just test and see how it goes for eth2 only:

suricata -c /etc/suricata/suricata.yaml -v --af-packet=eth2

...easy and flexible.