Firewall Wizards: RE: Shomiti Taps, Cisco Port Mirroring and IDS

["franks" <franks () nfr com>]

The thing to use is a media converter, (honestly I'm not sure who makes
them)
Or use a OS that can help 're-integrate' the signal. I think that a BSD
box with two nic's can do this [I think]

-----Original Message-----
From: firewall-wizards-admin () nfr com
[mailto:firewall-wizards-admin () nfr com] On Behalf Of Paul Cardon
Sent: Friday, January 04, 2002 6:43 AM
To: Don Ng
Cc: firewall-wizards () nfr net
Subject: Re: [fw-wiz] Shomiti Taps, Cisco Port Mirroring and IDS

Don Ng wrote:

>  Hello all, just need some assistance on the issue of
> Shomiti taps. I have spoken to the vendors but they
> had to check ...
>  
>  I am looking at their Century taps that comes with 4
> ports.
>  Two ports are used to place the device inline with
> the segment to be monitored.
>
> Original
>   Router-----Firewall
> After
>   Router----<P 1> Century TAP <Port 2>---Firewall
>                   |         |
>                  <P 3>    <P 4>
> The vendors advised me that for the other 2 ports, I
> was told that each port mirrored out one direction
> flow. Eg. Router --->Firewall for Port 3 and 
> Firewall---> Router for Port 4.
>
>  From the looks of things I would have to connect both
>
> Port 3 and 4 to another Hub and plugging an network
> IDS into that hub.
>
>  Router----<P 1> Century TAP <Port 2>---Firewall
>                   |         |
>                  <P 3>    <P 4>
>                     |      |
>                      HUB
>                       |----NID-200
>
> Is this the optimal way to put an inline tap.
> Cisco port mirroring seems to work fine mirroing
> multiple ports to a single port connected to an IDS.

No, using a hub could lead to collisions and loss of packets when 
combining the two directions.  Use a switch that can queue the packets.

-paul


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