[Snort-users] Problem running Snort Inline

Anshuman Anil Deshmukh anshuman at ...16510...
Fri Feb 6 01:36:28 EST 2015

Hi James,

Thanks for your reply.

Even with the command snort --daq afpacket --daq-mode inline -i eth0:eth1 result is same. I already tried different options like providing the options from the command line as well as configuring the same in the snort conf file. But same result with that.

What else could be reason? Just for your information initially snort was installed with the Autosnort script. Later on it was upgraded to version is there anything to do with the daq configuration after snort upgrade?


From: James Lay [mailto:jlay at ...13475...]
Sent: Thursday, February 5, 2015 7:12 PM
To: snort-users at lists.sourceforge.net
Subject: Re: [Snort-users] Problem running Snort Inline

On Thu, 2015-02-05 at 06:40 +0000, Anshuman Anil Deshmukh wrote:

We have issues running Snort inline. This is the exact problem which is mentioned here - http://www.linuxforums.org/forum/debian-linux/200751-snort-inline.html (see log below).

We have setup the Snort inline (version which is compiled using switch --enable-sourcefire.

It says “Enabling inline operation” and then switches to IDS mode.

Our command line for running Snort:

/usr/local/snort/bin/snort -c /usr/local/snort/etc/snort_conf_rules.conf -i eth0:eth1 -Q --pid-path=/var/run which creates the bridge automatically. Both the interfaces doesn’t have IP addresses assigned.

We have already enabled following options for snort inline:

config policy_mode:inline

config daq: afpacket

config daq_mode: inline

config daq_var: buffer_size_mb=1024

preprocessor normalize_ip4

preprocessor normalize_tcp: ips ecn stream

preprocessor normalize_icmp4

preprocessor normalize_ip6

preprocessor normalize_icmp6

Under verdicts it shows 0% packets blocked. We have enabled couple of drop rules for BRUTE FORCE attack one of which is getting detected. Here is the snort output.

02/02-12:12:23.042082  [Drop] [**] [1:2019876:2] ET SCAN SSH BruteForce Tool with fake PUTTY version [**] [Classification: Detection of a Network Scan] [Priority: 3] {TCP} -> 00.00.00.:22 (IP addresses information removed)

But under verdicts it shows nothing blocked. Why??


      Allow:      4335107 ( 59.187%)

      Block:            0 (  0.000%)

Output says:

Enabling inline operation

Running in IDS mode

        --== Initializing Snort ==--

Initializing Output Plugins!

Initializing Preprocessors!

Initializing Plug-ins!


Information about our setup-

   ,,_     -*> Snort! <*-

  o"  )~   Version GRE (Build 149)

   ''''    By Martin Roesch & The Snort Team: http://www.snort.org/contact#team

           Copyright (C) 2014 Cisco and/or its affiliates. All rights reserved.

           Copyright (C) 1998-2013 Sourcefire, Inc., et al.

           Using libpcap version 1.4.0

           Using PCRE version: 7.8 2008-09-05

           Using ZLIB version: 1.2.3


/usr/local/snort/bin/snort --daq-list

Available DAQ modules:

pcap(v3): readback live multi unpriv

ipfw(v3): live inline multi unpriv

dump(v2): readback live inline multi unpriv

afpacket(v5): live inline multi unpriv


Please let me know in case any other information is required.



>From snort-

Configuring Snort

Assuming that you did not disable static modules or change the default DAQ
type, you can run Snort just as you always did for file readback or sniffing an
interface.  However, you can select and configure the DAQ when Snort is invoked
as follows:

    ./snort \
        [--daq <type>] \
        [--daq-mode <mode>] \
        [--daq-dir <dir>] \
        [--daq-var <var>]

    config daq: <type>
    config daq_dir: <dir>
    config daq_var: <var>
    config daq_mode: <mode>

    <type> ::= pcap | afpacket | dump | nfq | ipq | ipfw
    <mode> ::= read-file | passive | inline
    <var> ::= arbitrary <name>=<value> passed to DAQ
    <dir> ::= path where to look for DAQ module so's

And from the daq README:


afpacket functions similar to the pcap DAQ but with better performance:

    ./snort --daq afpacket -i <device>
            [--daq-var buffer_size_mb=<#MB>]
            [--daq-var debug]

If you want to run afpacket in inline mode, you must craft the device string as
one or more interface pairs, where each member of a pair is separated by a
single colon and each pair is separated by a double colon like this:


or this:

I think you want:  snort --daq afpacket --daq-mode inline -i eth0:eth1

I believe -Q and --daq-mode inline work about the same.  Hope that helps.


"Legal Disclaimer: This electronic message and all contents contain information from Cybage Software Private Limited which may be privileged, confidential, or otherwise protected from disclosure. The information is intended to be for the addressee(s) only. If you are not an addressee, any disclosure, copy, distribution, or use of the contents of this message is strictly prohibited. If you have received this electronic message in error please notify the sender by reply e-mail to and destroy the original message and all copies. Cybage has taken every reasonable precaution to minimize the risk of malicious content in the mail, but is not liable for any damage you may sustain as a result of any malicious content in this e-mail. You should carry out your own malicious content checks before opening the e-mail or attachment." www.cybage.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.snort.org/pipermail/snort-users/attachments/20150206/46de78d6/attachment.html>

More information about the Snort-users mailing list