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On my Cisco Catalyst 3850 there is a SFP Module which is connected to another device, the port on the Other device (vendor equipment) come up but my interface is still down. The DOM Information show me receive and transmit pegel and if I do a shut command on that interface the other side goes down.

This is the config of that port:

interface GigabitEthernet1/0/8
 description port1
 no switchport
 ip address 10.1.1.80 255.255.255.254
end

But the port is still down:

sh int gi1/0/8 status

Port      Name               Status       Vlan       Duplex  Speed Type 
Gi1/0/8   port1   notconnect   routed       full   1000 1000BaseLX SFP

And on transceiver detail page there is everything fine:

#sh int gi1/0/8 transceiver detail   
ITU Channel not available (Wavelength not available),
Transceiver is internally calibrated.
mA: milliamperes, dBm: decibels (milliwatts), NA or N/A: not applicable.
++ : high alarm, +  : high warning, -  : low warning, -- : low alarm.
A2D readouts (if they differ), are reported in parentheses.
The threshold values are calibrated.

                              High Alarm  High Warn  Low Warn   Low Alarm
          Temperature         Threshold   Threshold  Threshold  Threshold
Port       (Celsius)          (Celsius)   (Celsius)  (Celsius)  (Celsius)
--------- ------------------  ----------  ---------  ---------  ---------
Gi1/0/8     39.7                95.0        90.0       -40.0      -45.0

                              High Alarm  High Warn  Low Warn   Low Alarm
           Voltage            Threshold   Threshold  Threshold  Threshold
Port       (Volts)            (Volts)     (Volts)    (Volts)    (Volts)
---------  ---------------    ----------  ---------  ---------  ---------
Gi1/0/8    3.32                  3.60        3.50        3.10       3.00

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Transmit Power     Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
---------  -----------------  ----------  ---------  ---------  ---------
Gi1/0/8     -5.2                -1.0        -1.9       -10.0      -11.0

           Optical            High Alarm  High Warn  Low Warn   Low Alarm
           Receive Power      Threshold   Threshold  Threshold  Threshold
Port       (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
-------    -----------------  ----------  ---------  ---------  ---------
Gi1/0/8     -6.8                -1.9        -2.9       -24.9      -26.0

I change the SFP Module but still the same, also change the port with the same result. How can I troubleshoot this issue.

It is a little bit strange to me that the Port on the other device comes up but my device is still down.

5
  • Is it single or duplex fibre ? If duplex, maybe one fiber is broken, so your SFP don't see the light from peer and stay down. As the other fiber is OK, the peer goes up (it received the light)
    – Dom
    Sep 16, 2019 at 6:29
  • The peer side can see my transmit and if he shut his device down the receive power goes down on my side. We also change the fibre. (it is duplex fibre)
    – kockiren
    Sep 16, 2019 at 6:34
  • What's on the other side? I'd suspect that that port isn't really activated - no laser modulation, no carrier, no link.
    – Zac67
    Sep 16, 2019 at 8:52
  • The peer side is on a vendor equipment (juniper I think) but they told me that the port is up on there side and they can see if I do shutdown on my interface. What do you mean with no laser modulation? If I can see the Optical Receive Power they send me anything or I am wrong?
    – kockiren
    Sep 16, 2019 at 8:59
  • Do you check the logs of the switch after shutdown/no shutdown ?
    – Dom
    Sep 16, 2019 at 14:55

1 Answer 1

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Vendors like to disable everything left to chance. Use speed nonegotiate to bring the link up.

1
  • Speed nonegotiate was the right solution. The port is up now.
    – kockiren
    Sep 23, 2019 at 9:48

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