[Snort-users] Snort not seeing all traffic?

Matt Kettler mkettler at ...4108...
Wed Apr 23 14:45:20 EDT 2003


First question:

Is the "hub" a 10/100 dual-speed hub?

If so:
  what speed is the interface from the hub to router?
  what speed is the interface from the hub to the switch?
  what speed is the interface from the hub to eth1 on the IDS box?

If all three numbers are not the same, that's your problem. The 10/100 
"auto switching" hubs are network-wise equivalent to a pair of hubs 
connected by a 2-port switch (also called an ethernet bridge if you want to 
get technical about it, and some of these hubs call themselves "auto 
bridging" instead of "auto switching")

10mbit hub      ----- switch ------- 100 mbit hub

Thus if there's mismatch in speeds (ie: the snort box is the only 100mbit 
connection and the other 2 are 10mbit), it won't actually see the traffic 
because of the internal switch between the two speeds.

At 03:17 PM 4/23/2003 -0400, Patrick Jones wrote:
>Snort 1.9.1
>Red Hat 8.0
>2 NICs
>Eth0 10.x.x.x
>Eth1 no address
>Installed ACID
>
>Topology:
>Router - Hub - Switch - Firewall - Internal Network
>           |                          |
>           |                          |
>         (Eth1)                       |
>         IDS(eth0)------------------/





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