Solved: Cisco SG300-28PP phantom link 'up' status when no cables plugged in

donbuckley · ‎09-30-2020

Hey all,

My SG300-28PP started misbehaving, whereby the 2nd bank of ports 7-12,19-24 stopped working. I've replaced the production switch and I am currently working on the problem switch on my workbench here. The switch is showing a number of ports as being operationally up with link, but nothing is physically plugged into them.

uplink for the switch is in gi1

voip phone is in gi2

the rest 3-24 copper ports are physically empty. (gi25-28 not depicted)

1	2	3	4	5	6
13	14	15	16	17	18

7	8	9	10	11	12
19	20	21	22	23	24

Things I've tried:

factory reset
upgraded fw to latest (no change when booting from last 2 firmware versions)
SW version 1.4.11.5 ( date 08-Apr-2020 time 13:49:34 )
Boot version 1.3.5.06 ( date 21-Jul-2013 time 15:12:10 )
HW version V02
disabled macros globally and on each port individually
admin shutdown / no shutdown all ports except the uplink in gi1 and the voip phone in gi2

switch#sh int config
Flow Admin Back Mdix
Port Type Duplex Speed Neg control State Pressure Mode
-------- ------------ ------ ----- -------- ------- ----- -------- ----
gi1 1G-Copper Full 1000 Enabled Off Up Disabled Auto
gi2 1G-Copper Full 1000 Enabled Off Up Disabled Auto
gi3 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi4 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi5 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi6 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi7 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi8 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi9 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi10 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi11 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi12 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi13 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi14 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi15 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi16 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi17 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi18 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi19 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi20 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi21 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi22 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi23 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi24 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi25 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi26 1G-Copper Full 1000 Enabled Off Down Disabled Auto
gi27 1G-Combo-C Full 1000 Enabled Off Down Disabled Auto
gi28 1G-Combo-C Full 1000 Enabled Off Down Disabled Auto

switch#sh int stat
Flow Link Back Mdix
Port Type Duplex Speed Neg ctrl State Pressure Mode
-------- ------------ ------ ----- -------- ---- ----------- -------- -------
gi1 1G-Copper Full 1000 Enabled Off Up Disabled On
gi2 1G-Copper Full 1000 Enabled Off Up Disabled Off
gi3 1G-Copper -- -- -- -- Down -- --
gi4 1G-Copper -- -- -- -- Down -- --
gi5 1G-Copper -- -- -- -- Down -- --
gi6 1G-Copper -- -- -- -- Down -- --
gi7 1G-Copper -- -- -- -- Down -- --
gi8 1G-Copper -- -- -- -- Down -- --
gi9 1G-Copper -- -- -- -- Down -- --
gi10 1G-Copper -- -- -- -- Down -- --
gi11 1G-Copper -- -- -- -- Down -- --
gi12 1G-Copper -- -- -- -- Down -- --
gi13 1G-Copper -- -- -- -- Down -- --
gi14 1G-Copper -- -- -- -- Down -- --
gi15 1G-Copper -- -- -- -- Down -- --
gi16 1G-Copper -- -- -- -- Down -- --
gi17 1G-Copper -- -- -- -- Down -- --
gi18 1G-Copper -- -- -- -- Down -- --
gi19 1G-Copper -- -- -- -- Down -- --
gi20 1G-Copper -- -- -- -- Down -- --
gi21 1G-Copper -- -- -- -- Down -- --
gi22 1G-Copper -- -- -- -- Down -- --
gi23 1G-Copper -- -- -- -- Down -- --
gi24 1G-Copper -- -- -- -- Down -- --
gi25 1G-Copper -- -- -- -- Down -- --
gi26 1G-Copper -- -- -- -- Down -- --
gi27 1G-Combo-C -- -- -- -- Down -- --
gi28 1G-Combo-C -- -- -- -- Down -- --

ports 3-28 are administratively down and nothing plugged into them physically at all.

now I bring them up:

switch(config)#int r gi3-28
switch(config-if-range)#no shut
08-Apr-2020 11:38:17 %LINK-I-Up: gi7
08-Apr-2020 11:38:17 %LINK-I-Up: gi8
08-Apr-2020 11:38:17 %LINK-I-Up: gi9
08-Apr-2020 11:38:17 %LINK-I-Up: gi10
08-Apr-2020 11:38:17 %LINK-I-Up: gi11
08-Apr-2020 11:38:17 %LINK-I-Up: gi12
08-Apr-2020 11:38:17 %LINK-I-Up: gi19
08-Apr-2020 11:38:17 %LINK-I-Up: gi20
08-Apr-2020 11:38:17 %LINK-I-Up: gi21
08-Apr-2020 11:38:17 %LINK-I-Up: gi22
08-Apr-2020 11:38:18 %LINK-I-Up: gi23
08-Apr-2020 11:38:18 %LINK-I-Up: gi24
switch(config-if-range)#08-Apr-2020 11:38:21 %STP-W-PORTSTATUS: gi7: STP status Forwarding
08-Apr-2020 11:38:21 %STP-W-PORTSTATUS: gi8: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi9: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi10: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi11: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi12: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi19: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi20: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi21: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi22: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi23: STP status Forwarding
08-Apr-2020 11:38:22 %STP-W-PORTSTATUS: gi24: STP status Forwarding

what in the lalalala with the forwarding (?) there is physically nothing plugged into anything from 3-28

switch(config-if-range)#exit
switch(config)#exit
switch#sh int stat
Flow Link Back Mdix
Port Type Duplex Speed Neg ctrl State Pressure Mode
-------- ------------ ------ ----- -------- ---- ----------- -------- -------
gi1 1G-Copper Full 1000 Enabled Off Up Disabled On
gi2 1G-Copper Full 1000 Enabled Off Up Disabled Off
gi3 1G-Copper -- -- -- -- Down -- --
gi4 1G-Copper -- -- -- -- Down -- --
gi5 1G-Copper -- -- -- -- Down -- --
gi6 1G-Copper -- -- -- -- Down -- --
gi7 1G-Copper Full 1000 Enabled Off Up Disabled On
gi8 1G-Copper Full 1000 Enabled Off Up Disabled On
gi9 1G-Copper Full 1000 Enabled Off Up Disabled On
gi10 1G-Copper Full 1000 Enabled Off Up Disabled On
gi11 1G-Copper Full 1000 Enabled Off Up Disabled On
gi12 1G-Copper Full 1000 Enabled Off Up Disabled On
gi13 1G-Copper -- -- -- -- Down -- --
gi14 1G-Copper -- -- -- -- Down -- --
gi15 1G-Copper -- -- -- -- Down -- --
gi16 1G-Copper -- -- -- -- Down -- --
gi17 1G-Copper -- -- -- -- Down -- --
gi18 1G-Copper -- -- -- -- Down -- --
gi19 1G-Copper Full 1000 Enabled Off Up Disabled On
gi20 1G-Copper Full 1000 Enabled Off Up Disabled On
gi21 1G-Copper Full 1000 Enabled Off Up Disabled On
gi22 1G-Copper Full 1000 Enabled Off Up Disabled On
gi23 1G-Copper Full 1000 Enabled Off Up Disabled On
gi24 1G-Copper Full 1000 Enabled Off Up Disabled On
gi25 1G-Copper -- -- -- -- Down -- --
gi26 1G-Copper -- -- -- -- Down -- --
gi27 1G-Combo-C -- -- -- -- Down -- --
gi28 1G-Combo-C -- -- -- -- Down -- --

so this second bank of ports, 7-12 and 19-24 is flaky.

furthermore, when I reboot the switch, only the first bank of ports 1-6 and 13-18, light up. the second bank doesn't light up.

So my takeaway is that the second bank is unstable.and buy a new switch. Am I right or can I fix this somehow with some heavy duty firmware / boot reinstall etc

I'm going to leave this switch with the 2nd bank administratively down, clear the logs and let it sit overnight and see what happens tomorrow.

any advice?

Sujoy Paria · ‎10-01-2020

Hi,

It seems like reported ports are gone faulty. You may try to open a service request following the below mentioned link for hardware support…

https://www.cisco.com/c/en/us/support/web/tsd-cisco-small-business-support-center-contacts.html

View solution in original post

Sujoy Paria · ‎10-01-2020

Hi,

It seems like reported ports are gone faulty. You may try to open a service request following the below mentioned link for hardware support…

https://www.cisco.com/c/en/us/support/web/tsd-cisco-small-business-support-center-contacts.html

donbuckley · ‎10-01-2020

Thanks,
I've already replaced this switch so I will just keep it out of production. Not worth the time it takes to repair it :0)