[c-nsp] PoE switches and biometric devices (strange behaviour)

[Amol Sapkal]

Hi all,

Here is the setup:
I have a PoE switch, which is connected to 2 other PoE switches.
All switches are cat 3560 switches (WS-C3560G-48PS)
Biometric devices (Finger-printers) connect on to one port of each downlink
switches (there are 2 downlink switches)
I have disabled inline power on all the ports of these 3 switches, as there
are no PoE devices connected
The uplink cables for the downlink switches are CAT6 and under 20m.
All access ports are marked as portfast (including the biometric device's
port)
IOS: 12.2(35)SE5 (IP Services)

Before the inline power was disabled, one of the switches displayed an
inline power error for the biometric device's port, which on further checks
with cisco.com, pointed to the bug CSCeb24148 (related to Electro-static
Discharge). Since then, I have upgraded the IOS, as per the recommendations.

The problem:
Before inline power was disabled, the biometric device port went down,
without any logs (apart from the inline power error, which was generated
only once in multiple port checks).  Also, the reliability of the port goes
down to 254/255. After the IOS upgrade, the switch no longer throws up the
inline power issue. As a precaution, I disabled inline power on all ports
using the 'power inline never' command.

Still, the biometric device disconnected.

Post that, the following was done:
Cabling was changed/verified
Trunking was disabled (as this was a cascade environment with no vlans, it
did not make any difference - all 3 switches belong to a single broadcast
domain)
Various duplex/speed combinations were tested
Non-PoE switches were tested in standalone modes, and they did not
disconnect the biometric device.
 Non-PoE switches were tested in standalone modes, and in the same cabling
closet and they did not disconnect the biometric device (to verify static
charges issues)
When cascaded with PoE switches, the non-PoE switched disconnected the
biometric device!
The switches were configured to NOT errdisable a port on detecting a
loopback

None of the above helped.

Now, I get the following logs on the non-PoE switch (3560), before the
biometric device's port disconnects:

04:19:26: ILP Start PHY Cisco IP phone detection ( Fa0/48 ) Okay
04:19:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/48,
changed state to down
04:19:28: %LINK-3-UPDOWN: Interface FastEthernet0/48, changed state to down

I fail to understand as to why the non-PoE switch is trying to detect a
cisco IP phone, on a port to which the biometric device connects (port
fa0/48). This is inspite the fact that the uplink switch has been configured
to disable inline power on all ports, including the downlink port. Even, the
other downlink switch is configured to disable inline power.

Question: Can anyone kindly help me to understand the above behaviour?
Question 2: How can I disable the detection of the Cisco IP phone on any
PoE/non-PoE switch?

Another thing that I am unable to figure out is the possibility of static
charge generation in the cabling closet.


-- 
Warm regards,

Amol Sapkal

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