Snort mailing list archives

Re:Snort on span port


From: SN ORT <snort_on_acid () yahoo com>
Date: Mon, 16 Aug 2004 06:31:33 -0700 (PDT)

Wow. That's exactly what I said. I think he got it
already. Oh but wait, what happened to the "problem"
with the 5500 spanning?


My quote:
Ok, so if I remember correctly, ---NO I DID NOT
REMEMEBER CORRECTLY-- root-bridges are
like
only for vlan trunking protocol and elections and
what-not of switches that will act as root bridges.
All they do is keep track of vlans. ** Not sure what
this
has to do with port spanning/monitoring.**  Your
engineers should be spannig at the physical layer
and
not the vlan layer. ** They should be spanning the
physical ports that the vlans are trunked on and
connected to each other.**  Nevermind the gibberish
about
Cisco switches not keeping up with
spanning...hogwash!
You assign vlans and trucks to ports, all the
engineers need to worry about are physically
spannning
those ports to your ports.

IOW, let's say my trunk port is port one on one of
the
switches. The port is either part of the backbone or
at least connects to the other switches. Now let's
say
your IDS is connected to port two. All the engineer
has to do is get on the switch, go to port 2 and
type
in "port monitor fa0/1" Then you'd be set!


Message: 3
Date: Sat, 14 Aug 2004 13:35:13 -0700
From: Charles Heselton <charles.heselton () gmail com>
Reply-To: Charles Heselton
<charles.heselton () gmail com>
To: snort-users () lists sourceforge net
Subject: Fwd: [Snort-users] Snort on span port

A solution presented by one of my network engineers.


---------- Forwarded message ----------
From: Lohr, Corey R <corey.lohr () nmci-isf com>
Date: Thu, 12 Aug 2004 23:54:40 -0700
Subject: RE: [Snort-users] Snort on span port
To: "Garrett, Joshua" <joshua.garrett () nmci-isf com>,
"Sheldon, Mike
E." <mike.sheldon () nmci-isf com>, Charles Heselton
<charles.heselton () gmail com>, "O'Sullivan, Richard"
<richard.o'sullivan () nmci-isf com>


Josh and Mike are right and it has nothing to do
with root bridge
selection (tha. The 0.2 Mbps of traffic is switching
overhead (bpdu,
hello frames/packets, dot1q/isl frames, and pagp if
channeling is
configured). The following would fix the problem:
 
+++++         +++++  
+ sw1+ -----+ sw2+
+++++         +++++
     |                   |
     |                   |
+++++          +++++       ++++++
+ sw3+ -----+ sw4+-----+sniffer+
+++++          +++++       ++++++
 
Setup an rspan on sw1, sw2 and sw3 with source
port(s) and vlan(s) to
destination switchport x on sw4.
 
Then configure sw4 with a regular span including all
the source
switchports and vlan(s) coming from sw1, sw2 and sw3
to destination
switchport y on sw4.
 
VACLs are used for filter granularity once all span
requirements have
been configured to cut down on layer 2 overhead.
 
-C


 

<snip>

Haw haw!

Marc


                
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