You can clear the NetFlow cache manually, FYI - 'clear ip cache', I
believe.
What IOS/platform are you running on the box that's seeing the
NetFlow? At what point in the topology is it located?
If the router is running a recent T-train image, there's a feature
called 'RITE' which is essentially SPAN for the router - you could
connect your tcpdump box there and sniff the traffic to see if the
traffic is present.
l2trace should work if you have the actual MAC address of the box(es)
in question; but again, that info might be spoofed or mangled.
Again, on what input/output interfaces are you seeing the traffic in
NetFlow? Can you paste 'sh ip cache flow' output?
Feel free to contact me 1:1 if that would help.
On Apr 11, 2006, at 7:12 AM, Stef wrote:
UPDATE:
Thanks to all who replied, and continue(d) with suggestions. We still
have not been able to isolate the problem - the attempt is now to shut
down one port at a time, and watch netflow to see when it stops (we
are waiting for each port for a 2 * cache expiration, so that we do
not risk to move past the "guilty" port). No span/monitor session
revealed the needed info, either going through each port, entire VLAN,
etc. Shutting down ports has an impact on production, though, so it
has to be done fast, and coordinated with the end points, so it has
been moving slow (thus the lack of a follow-up, lately). We are beyond
66% of the ports, and still have not isolated it, so it may be - in
the end - a faulty flow record, as someone already suggested.
As far as this latest recommendation - I wish we had the MAC ;) - this
whole exercise is an attempt to identify it, after which I am pretty
sure "game over"!
Stef
On 4/11/06, AJ Cochenour <ajc@mytcpip.net> wrote:
Assuming CatOS on the C4506:
1. Issue the following to locate port if host may be directly
connected:
'sh cam dynamic | include <Questionable Source MAC --
FF-FF-FF-FF-FF-FF>'
2. If operating within distributedswitch network issue the following
(assuming Cisco/Foundry topology):
'l2trace <Switch MAC -- FF-FF-FF-FF-FF-FF> <Questionable
Source MAC
-- FF-FF-FF-FF-FF-FF>' to reveal L2 path to device(s) in question.
If using IOS on C4506 issue the following to locate port if host
may ne
directly connected:
'sh mac-address-table | include <Questionable Source MAC --
FF-FF-FF-FF-FF-FF>'
In the absence of recent CatOS/IOS firmware to support the commands
provided TCL scripting would be a viable alernative. Happy hunting
AJC
ajc@mytcpip.net
Combining the below from Nicolai with setting up the port in
promiscuous
mode and running a Network Sniffer tool would give you enough
data to
track it down, I would think.
-
Jean-Raymond Xavier Pierre
Scientific Computing and Computing Services
Stanford Linear Accelerator Center
-----Original Message-----
From: Nicolai van der Smagt [mailto:nicolai.vandersmagt@bbned.nl]
Sent: Monday, April 10, 2006 2:12 AM
To: stefmit@gmail.com
Cc: incidents@lists.securityfocus.com
Subject: Re: Bogon IPs traffic only seen by netflow, confined
within a
VLANonly
Stef,
Why don't you just span the entire VLAN to a machine capable of
running
tcpdump, use tcpdump -e to find the hardware address of the
station(s)
sending the traffic, and look up that address in the CAM table of
your
switch? Would be quicker than spanning 1 port at a time..
Kr,
Nicolai van der Smagt
-----
I have a question, that - in case someone has seen this somewhere
- may
save us a lot of work: our netflow tool has been reporting lots
of traffic
(100s of MB/day) between some bogon IPs: 0.10.94.27 to a few IPs
in the
37.245.0.0/24 network (e..g 37.245.0.64, 37.245.0.18,
37.245.0.14, etc.).
The report comes exclusively for one VLAN, from a
4506 switch. The IP protocols being reported are not among the
well known
ones (TCP, UDP, ICMP, etc.), but rather #140 (for the majority of
traffic)
and #63 (and some other ones). We have tried to reach (ICMP echo,
nmap,
etc.) those IPs from various stations from the same VLAN, with no
success.
Monitoring a few ports (span to a probe), at random, have not
revealed any
ARP traffic for those IPs, either, thus
- at this stage - being unable to determine who is responsible
for that
traffic. The default gateway for all the systems on that VLAN
does not see
any of this traffic, either - and neither any other systems form
that
point on, upstream, al the way to the internal interface of the
firewall,
which makes us think that somehow that odd traffic is really
confined to
that specific VLAN (thus - probably - some sort of spoofing,
combined with
systems aware of each other's MAC, thus no need to hit the
gateway ...).
The next step is to write a script on the switch itself (TCL -
probably) or on an external probe, so that we could span/monitor
one port
at a time, and go through all the ports on all blades from that
4506 (4 modules * 48 ports), until the probe hooked up t the
destination
port will report the traffic we are looking for (as netflow data
reports
this traffic going on continuously - so it must exist at all
times), from
one of the ports. Another simpler approach (but unfeasible,
unfortunately,
in our scenario, due to the need for machines to be up 3 shifts/
day) would
be to shut down one system at a time, and watch netflow when it
stops
reporting this junk.
So ... short of doing one of the above - has anybody seen this
before?
Do you have an idea of how else we could trace down the perpetrator?
----------------------------------------------------------------------
Roland Dobbins <rdobbins@cisco.com> // 408.527.6376 voice
Everything has been said. But nobody listens.
-- Roger Shattuck
