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SG300 Stacking and Powered from POE by Upstream Switch

Jarrett Cadiz
Level 1
Level 1

Hi Everyone,

I searched on Google for this unique behavior I discovered on a pair of SG300-28P.

On a second switch (ver 1.2.7.76) when I unplugged the power cord, to my amazement the switch turned right back on (about 1 second later), with the power cord removed. To verify that the power is indeed coming from POE, the upstream switch (ver 1.1.2.0) that is the same model (sg-300-28p), shows all 7 Ethernet ports connecting the two drawing from 2700mW, to 3000mW.

While the second switch is powered from the first over POE, the POE does not work on the second switch to power anything, and the system summary mentions something about "PoE Power Information on Master Unit".

What kind of mode is this?

Is this a stacking operation, and is POE on the second switch NOT supposed to work when powered over Ethernet from an upstream switch?

Thanks!

Jarrett

Jarrett http://www.jarrettcadiz.com http://www.cloudchase.net/company/jarrettcadiz
2 Replies 2

Tom Watts
VIP Alumni
VIP Alumni

Hi Jarret, can you make a diagram how you are interconnecting these units? Additionally,  can you take a digital photo showing the switch powered while capturing the power cord unplugged? Please post a show power inline for each unit as well.

-Tom Please mark answered for helpful posts http://blogs.cisco.com/smallbusiness/

Hi Thomas,
Thank you for your response, here is a small diagram of the connection between the two switches.

[GBE 3-1– SG-300-28P]

      | - From Ports 1, 4, 5, 7, 8, 11, 16

      |

      |  - (Trunk)

      | - To Ports 1-4, 16-18

[GBE 4-1– SG-300-28P]

The show power inline output on both switches:

GBE3-1

Port based power-limit mode

Unit  Power  Nominal Power   Consumed Power   Usage Threshold   Traps

---- ------- ------------- ------------------ --------------- ---------

1     On      180 Watts     81 Watts (45%)         95         Disable

  Port      Powered Device         State          Status    Priority   Class

-------- -------------------- ---------------- ------------ -------- ---------

  gi1                               Auto            On        low     class0

  gi2                               Auto        Searching     low     class0

  gi3                               Auto        Searching     low     class0

  gi4                               Auto            On        low     class0

  gi5                               Auto            On        low     class0

  gi6                               Auto        Searching     low     class0

  gi7                               Auto            On        low     class0

  gi8                               Auto            On        low     class0

  gi9                               Auto        Searching     low     class0

  gi10                              Auto            On        low     class3

  gi11                              Auto            On        low     class0

  gi12                              Auto            On        low     class3

  gi13                              Auto            On        low     class0

  gi14                              Auto            On        low     class0

  gi15                              Auto            On        low     class3

  gi16                              Auto            On        low     class0

  gi17                              Auto        Searching     low     class0

  gi18                              Auto            On        low     class0

  gi19                              Auto            On        low     class0

  gi20                              Auto        Searching     low     class0

  gi21                              Auto        Searching     low     class0

  gi22                              Auto        Searching     low     class0

  gi23                              Auto        Searching     low     class0

  gi24                              Auto            On        low     class0

GBE4-1

Port based power-limit mode

Unit  Power  Nominal Power   Consumed Power   Usage Threshold   Traps

---- ------- ------------- ------------------ --------------- ---------

1     On      180 Watts      0 Watts (0%)          95         Disable

  Port      Powered Device         State          Status    Priority   Class

-------- -------------------- ---------------- ------------ -------- ---------

  gi1                               Auto          Fault       low     class3

  gi2                               Auto          Fault       low     class3

  gi3                               Auto          Fault       low     class3

  gi4                               Auto          Fault       low     class3

  gi5                               Auto          Fault       low     class3

  gi6                               Auto          Fault       low     class3

  gi7                               Auto          Fault       low     class3

  gi8                               Auto          Fault       low     class3

  gi9                               Auto          Fault       low     class3

  gi10                              Auto          Fault       low     class3

  gi11                              Auto          Fault       low     class3

  gi12                              Auto          Fault       low     class3

  gi13                              Auto          Fault       low     class3

  gi14                              Auto          Fault       low     class3

  gi15                              Auto          Fault       low     class3

  gi16                              Auto          Fault       low     class3

  gi17                              Auto          Fault       low     class3

  gi18                              Auto          Fault       low     class3

  gi19                              Auto          Fault       low     class3

  gi20                              Auto          Fault       low     class3

  gi21                              Auto          Fault       low     class3

  gi22                              Auto          Fault       low     class3

  gi23                              Auto          Fault       low     class3

   gi24                              Auto          Fault       low     class3

The picture of the switch powered on while it is unplugged.

Thank you,

Jarrett
http://www.jarrettcadiz.com
http://www.cloudchase.net/company/jarrettcadiz

Jarrett http://www.jarrettcadiz.com http://www.cloudchase.net/company/jarrettcadiz
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