Snort mailing list archives
Re: Question about Inline mode
From: John Liss <john () lissproductions com>
Date: Mon, 05 Dec 2011 10:00:38 -0700
Helpful as they were, I still have the following questions. When using either NFQ or the DAQ modules, are the interfaces bonded together? I completely understand that the Management interface is assigned an IP Address, a gateway and a network (subnet mask). What happens to the two interfaces used in inline mode? If I place the sensor inline, are the interfaces numbered? DO I need to fully provide networking (routing) between the interfaces?
With --daq afpacket, the pair of interfaces become a bridge. Setup on ubuntu 10.04: The interface setup: auto eth0 iface eth0 inet manual up ifconfig $IFACE <your mgt ip> up auto eth1 iface eth1 inet manual up ifconfig $IFACE 0.0.0.0 up up ip link set $IFACE promisc on down ip link set $IFACE promisc off down ifconfig $IFACE down auto eth2 iface eth2 inet manual up ifconfig $IFACE 0.0.0.0 up up ip link set $IFACE promisc on down ip link set $IFACE promisc off down ifconfig $IFACE down Running snort: /usr/local/bin/snort --daq afpacket -Q -c /etc/snort/snort.conf -i eth1:eth2 -D Network on eth1, becomes the same network on eth2, known as a bridge. It works wonderfully and drops packets as advertised.
Does the inline mode require two interfaces? Can Snort support multiple networks, simultaneously? Does this reduce the throughput capability of the monitor?
Inline requires two interfaces. Internet router <-> eth1 <- snort -> eth2 <-> firewall <-> internal. Yes you can run multiple networks on a single box. You just need enough horse power in the box for snort to keep up with the traffic, and enough interfaces to act as bridges. Example: You have a monster box with 10 network cards in it, and enough cpu/memory to run multiple instances of snort. You would just run snort over the interfaces: Network setup: eth0 = management. eth1:eth2 = first bridge. eth3:eth4 = second bridge. eth5:eth6 = third bridge. eth7:eth8 = fourth bridge. etc... Snort setup: /usr/local/bin/snort --daq afpacket -Q -c /etc/snort/snort1.conf -i eth1:eth2 -D /usr/local/bin/snort --daq afpacket -Q -c /etc/snort/snort2.conf -i eth3:eth4 -D /usr/local/bin/snort --daq afpacket -Q -c /etc/snort/snort3.conf -i eth5:eth6 -D etc... I personally would still tend to lean towards 4 individual boxes in production environments. That way if you loose a box for whatever reason, one network segment is only affected. Development or test networks where traffic isn't critical, sure, toss them all on one box. (But who has one of those? My networks are all classified as must have up.) -John
Multiple networks can be supported but of course band width is the consideration here along with the strength of the Snort sensor. There are better people on this list to answer than me but depending on the size/bandwidth considerations you may want to consider using 4 sensors that report to a main server for analysis. Like I said, others on this list can help there as I have no experience here. Search the Google Groups list too.Four sensors and a Main Server is an exceptional idea. Thank you for that. From reading the above sites listed, it would seem that afpacket is the method to use for inline use. Is there a consensus here?Hope this serves at least as a start to answer your questions. Bill
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Current thread:
- Question about Inline mode Albert E. Whale (Dec 04)
- Re: Question about Inline mode NA (Dec 04)
- Re: Question about Inline mode Albert E. Whale (Dec 04)
- Re: Question about Inline mode Michael Altizer (Dec 04)
- Re: Question about Inline mode John Liss (Dec 05)
- Re: Question about Inline mode Albert E. Whale (Dec 04)
- Re: Question about Inline mode NA (Dec 04)