Snort mailing list archives

Re: $HOME_NET question


From: Matt Kettler <mkettler () evi-inc com>
Date: Wed, 22 Jan 2003 15:54:16 -0500

As per the comments in snort.conf, if you use $eth0_ADDRESS it uses the IP *and* netmask of eth0.

# or use global variable $<interfacename>_ADDRESS
# which will be always initialized to IP address and
# netmask of the network interface which you run
# snort at.
#
# var HOME_NET $eth0_ADDRESS

This in your case your home_net is likely going to be 192.168.1.2/24 which means that 192.168.1.* will be recognized as part of it.

At 12:13 PM 1/22/2003 -0800, Ralph Churchill wrote:
I have snort 1.8.7. I have set my $HOME_NET to be
$eth0_ADDRESS and my external net set to !$HOME_NET.
However, I still get alerts from other computers on my
subnet! For example, the "SNMP public access udp" rule
says:

alert udp $EXTERNAL_NET any -> $HOME_NET 161...

For this example, assume my IP is 192.168.1.2. I'm
getting  alerts for a packet from 172.20.39.32 to
192.168.1.3. Why?   I'm totally confused. I thought
$HOME, if set to $eth0_ADDRESS would only give alerts
for things coming into my IP?!?! Am I wrong?

RMC



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