C3850 port down with TX/RX optical power correctly seen

[M.Fly]

Hi,
we have a C3850 24XS with a SFP+ module connected to a DWDM on 1310nm standard port, 10G.

If the carrier shutdown the link, we have a down on port connected to DWDM, but we have optical power on RX, the same optical power with port in UP state.

Spoiler

Optical High Alarm High Warn Low Warn Low Alarm
Receive Power Threshold Threshold Threshold Threshold
Port (dBm) (dBm) (dBm) (dBm) (dBm)
--------- ----------------- ---------- --------- --------- ---------
Te2/0/23 -5.1 2.5 0.4 -14.4 -16.4

We see the optical in/out power but the port is in down state:

Spoiler

TenGigabitEthernet2/0/23 is down, line protocol is down (notconnect)
Hardware is Ten Gigabit Ethernet, address is 2c01.b57a.bd4a (bia 2c01.b57a.bd4a)

Maybe the problem is the SFP+ module? Or wathelse?

[balaji.bandi]

what is the SFP Module full information,  what device other side connected ? how far is the DWDM equipment ? what mode cable you using ?

what you see the log on the device when you connect the cable, is go up and immediately down ?

can you post - show inter  ten2/0/23 

[M.Fly]

The module is a SFP-10GBase-LR on 1310nm.
The other side is a L2 DWDM, we do not know the vendor of this equipment, is a Tier1 carrier.
The DWDM equipment is in the same data center, we use a cross connect with SMR Fiber.

When the carrier shutdown the circuit, we see immediately down, but the RX power still -5.1/-5.2 dbm, the same with port in UP state.

sh interfaces tenGigabitEthernet 2/0/23
TenGigabitEthernet2/0/23 is down, line protocol is down (notconnect)
Hardware is Ten Gigabit Ethernet, address is 2c01.b57a.bd4a (bia 2c01.b57a.bd4a)
Description: link-CITY-TO-CITY-TIS-10000006866
Internet address is 192.168.157.17/30
MTU 1500 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not set
Full-duplex, 10Gb/s, link type is force-up, media type is SFP-10GBase-LR
input flow-control is on, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 11:29:57, output hang never
Last clearing of "show interface" counters 10:56:42
Input queue: 0/375/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

Thank you.

[marce1000]

                                 >....When the carrier shutdown the circuit
 - May depend on how this is done , meaning if they only shutdown network protocols , then layer1 (link) may remain available , 

 M.

[M.Fly]

On a DWDM point-to-point link i suppose there are any network protocol, is a "fiber cable" from one end-point to another, like a physical cable.

[Leo Laohoo]

Plug a loopback cable or loop the optic -- Does the link light go on?

[M.Fly]

Yes, with a loop is OK, or with the circuiti in UP state, we have UP port with the same RX power on the SFP+ module, if the carrier shutdown the circuit, we have DOWN on port but RX power still the same.

[Leo Laohoo]

---

@M.Fly wrote:
we have DOWN on port but RX power still the same

---

If you loop the port, the Rx power is the same?

[M.Fly]

No, there isn't.

I have tested one more identical SFP+ in other device, and the DOM report correctly the optical power, and of course the no signal optical power of -40dbm

[balaji.bandi]

is this drect connection or via any patch pannel or comms room between DWDM and your device ?

[Leo Laohoo]

---

@M.Fly wrote:

No, there isn't.

I have tested one more identical SFP+ in other device, and the DOM report correctly the optical power, and of course the no signal optical power of -40dbm

---

Good.  This eliminate the issue with the optics.  Move the "loop" down to the cable path and re-do the test.  

[M.Fly]

Ok, we have the solution, but no problem on the switch.

The problem is that the trace picked up via monitor capture is on cpu level, the return packet with the loop have the same mac address of sending interface, the switch discard the packet with the same mac address before the cpu monitor capture function.

The problem is solved and the test with the loop and the monitor capture function is not the way, monitor capture take a pcap trace not on the hardware.

Many thanks to all.