[Snort-users] Snort as Gigabit Sensor

twig les twigles at ...131...
Thu Jul 24 12:15:07 EDT 2003


We are doing something similar.  6509 with a gig card (fiber
3com) doing more than 14Mb without a problem.  The box we are
using isn't even that big: 2 PIII 1GHz CPUs, 1 gig old sdram.  2
things we chose specifically that may help us are: 1. we use a
66MHz, 64-bit PCI slot instead of a normal 33MHz one, 2. we have
dual scsi controllers - one hard drive for the OS, one for the
data.  We also use FreeBSD, which I can't prove is faster than
RH but I have to say that we use it because that is a
significant difference between our setups.  No OS wars in my
name.

So I guess I'm dodging the RH9 tuning question but you may have
a bottleneck in the hardware.  Also if you can't even get 14Mb
of traffic without loss I'd check the cabling, switch interface,
NIC driver, etc. too, that is just a really low number.

--- Banniza Robert <Robert.Banniza at ...9244...> wrote:
> Anyone have any good pointers on tuning Linux (Redhat 9) as a
> gigabit
> sensor? Currently, we are using a Broadcom Corporation
> NetXtreme BCM5703
> Gigabit Ethernet (TG3 kernel module) Netgear card as the
> sniffing card. We
> have set up a span port so that we can see all traffic on a
> Cisco 6509. The
> sad thing is we are encountering 40% packet loss. The network
> interfaces
> were statically compiled into the kernel and /etc/sysctl.conf
> was modified
> with the following to provide larger buffers:
> 
> # increase Linux TCP buffer limits
> net.core.rmem_max = 8388608
> net.core.wmem_max = 8388608
> net.core.rmem_default = 65536
> net.core.wmem_default = 65536
> 
> # increase Linux autotuning TCP buffer limits
> net.ipv4.tcp_rmem = 4096 87380 8388608 
> net.ipv4.tcp_wmem = 4096 65536 8388608 
> net.ipv4.tcp_mem = 8388608 8388608 8388608
> 
> # flush window size
> net.ipv4.route.flush=1
> net.core.netdev_max_backlog=2500
> 
> We have not performed any rule tuning yet and the current
> sustained
> throughput we have seen through this connection is around 
> 14Mb which is
> nowhere close to gigabit speeds. Any ideas?
> 
> Thanks
> Robert
> 
> 
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