[Snort-users] Snort inline mode problem

Y M snort at ...15979...
Sun Aug 24 12:29:02 EDT 2014

Ok, assuming you are setup this way:
Internet <---> eth2 | IPS | eth1 <---> local, where eth1 and eth2 are the listening (promiscuous) interfaces and through which traffic is passing. When you force Snort into inline mode using afpacket, Snort (logically) bridges the interfaces together to let the traffic pass, otherwise drop it when matches occur. Looking again at the rule you have, both destinations are local. What happens if you change both destinations (HOME_NET and EXTERNAL_NET) to any/any? Better, take rule sid:384 and modify it and try to ping an external source and see what happens. For troubleshooting purposes only, run Snort with -A console or -A cmg so you can see whats going directly on the console (without -D).
Also, do you have normalization enabled?
Date: Sun, 24 Aug 2014 17:50:27 +0200
Subject: Re: [Snort-users] Snort inline mode problem
From: demonsdebason at ...11827...
To: snort at ...15979...
CC: snort-users at lists.sourceforge.net

Here is the setup:

INTERNET <--> | IPS/router | <--> | local machines |

IPS box has 4 interfaces, where 2 have an address, others don't. It seemed illogical to set Snort to listen on interfaces where no traffic is passing through.

When I set Snort it to use unaddressed interfaces, nothing happens meaning no alerts are recorded and ICMP echo test isn't working.
Tried setting up bride interfaces and assigning the two unaddressed interface to Snort, same results.

The only results I get is having Snort listening the interfaces traffic traverse though.

On Sun, Aug 24, 2014 at 4:24 PM, Y M <snort at ...15979...> wrote:

How are you testing/connecting the client (icmp echo request sender), the sensor, and the receiver of the icmp? The NICs that Snort is using to receive --> pass/drop --> forward traffic should be inline with no IP addresses. 

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