Snort mailing list archives

Snort Just Not Working With Shadow Interface


From: Rhugga <nagios-user () sandiego420 com>
Date: Tue, 20 Jul 2004 06:49:10 -0700

I will be as terse as possible here, because I have tried configs from people that claim they should work but aren't. I have read the documentatrion probably 5 times now, (well the documentation says version 1.0, the link on the website says 1.1, but the version I am using is 1.2)

Anyway. My system is vanilla RH 9 with all updates except I build my own openssl library and also using mysql 4.x in /usr/local. ( I have compeltely re-installed since I first started just to eliminate ANY possible issues because some people claim snort 1.2 works as I desire on RH 9)

eth0
-------------------------------
IP address: 10.250.200.33
Netmask: 255.255.255.0
SysKonnect Copper GB NIC directly connected to a switch in our Black Diamond. (Cat 6 cabling with no patch panels in between)

eth1
--------------------------------
IP address: None
Onboard Intel NIC connected to a 4 port hub. Also on this hub is a Cisco 3600 router and 2 Netscreen Firewalls.

The network on the hub is 65.120.XX.XX with netmask of 255.255.255.240

Here are the contents of the /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE=eth1
BOOTPROTO=static
ONBOOT=yes
IPADDR=0.0.0.0
NETMASK=0.0.0.0

Note: I added this after I initially tried to get it working without adding an IP. I saw this as a solution to some people's problems in the mailing list archvie.

If I look at the traffic on eth1:

syslog:/usr/local/snort/bin #./snort -i eth1 -v
Running in packet dump mode
Log directory = /var/log/snort

Initializing Network Interface eth1
OpenPcap() device eth1 network lookup:
       eth1: no IPv4 address assigned

       --== Initializing Snort ==--
Initializing Output Plugins!
Decoding Ethernet on interface eth1

       --== Initialization Complete ==--

-*> Snort! <*-
Version 2.1.3 (Build 27)
By Martin Roesch (roesch () sourcefire com, www.snort.org)
07/20-06:28:39.383108 207.158.24.130 -> 65.120.XX.XX
IPV6-CRYPT TTL:52 TOS:0x0 ID:43725 IpLen:20 DgmLen:104
=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+

07/20-06:28:39.383705 207.158.24.130 -> 65.120.XX.XX
IPV6-CRYPT TTL:52 TOS:0x0 ID:43726 IpLen:20 DgmLen:104
=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+

It is reading traffic on eth1. However, when I start nagios it will run, but it will not match anything. I get not a single alert. However, when I assign eth1 a valid IP address on the 65.120.XX.XX network, it immediately starts matching. Within seconds my alert count starts climbing. (Note that when I say I am assigning it a valid IP address I also modify HOME_NET to reflect this)

Here is how I define HOME_NET when I am trying to use snort _without_ an IP address: var HOME_NET [10.250.200.0/24,10.250.201.0/24,10.250.202.0/24,10.250.203.0/24,10.250.204.0/24,10.250.205.0/24,10.250.206.0/24,65.120.XX.0/28]
var EXTERNAL_NET any

What am I doing wrong? According to the documentation and the responses to my first emails, this config is correct.

What gives??

Thx,
Rhugga




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