RE: Bogon IPs traffic only seen by netflow, confined within a VLANonly

["Nyuk Loong Kiw" <Kiw () safecom co nz>]

Are all the netflow packets generated by the 4506 switch? Are you using
flowtools for netflow analysis? 

> From memory flows generated by cisco devices actually have the
additional interface identifier or something similar in the actual flow
packets itself, if you know which cisco interface is the 'incoming'
interface you should be able to apply a filter to look for all traffics
going through that incoming interface, that should help isolate things.


Kiw


-----Original Message-----
From: Stef [mailto:stefmit () gmail com] 
Sent: Wednesday, April 12, 2006 2:13 AM
To: incidents () lists securityfocus com
Subject: Re: Bogon IPs traffic only seen by netflow, confined within a
VLANonly

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?
#####################################################################################
Important: This electronic message and attachments (if any) are confidential
and may be legally privileged. If you are not the intended recipient do not
copy, disclose or use the contents in any way. Please let us know by return
e-mail immediately and then destroy this message.
#####################################################################################