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9/6/10

Digital Optical Monitoring

Hopefully, you're watching the link-up and link-down events for your infrastructure, at least on the plumbing links.  But how are you keeping track of the Layer 1 issues that impact traffic without actually taking the link down?

In the campus, one commonly ignored issue is Digital Optical Monitoring (DoM).  It has been ignored partially because the most common SFPs, GLC-SX-MM and GLC-LH-SM,  lack DoM support!  Luckily, as our 10 GigabitEthernet deployments grow, we're getting more DoM capable optics.

Keeping an eye on the Tx and Rx dBm values on optical links can save you a lot of headaches.  I've seen a few pinched fiber strands work just fine for weeks, then die at some odd hour when no one is around.  Wouldn't it be nice to get an SNMP trap when the levels are reaching marginal values?  Well, on many platforms you can.  The 6500 has had support for DoM SNMP traps since SXE! 

Here is the config to monitor DoM thresholds every 5 minutes and send a trap when the value crosses a threshold:

snmp-server enable trap transceiver
transceiver type all
 monitoring
 monitoring interval 300

And this is a convenient command to get the current values for all of your DoM supported optics:

6509-1#show interfaces transceiver detail
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)
---------- ------------------  ----------  ---------  ---------  ---------
Te1/1        33.0                74.0        70.0         0.0       -4.0
Te1/2        33.6                74.0        70.0         0.0       -4.0
Te1/5        36.0                74.0        70.0         0.0       -4.0
Te1/6        34.0                74.0        70.0         0.0       -4.0
Te2/1        30.0                74.0        70.0         0.0       -4.0
Te2/2        31.2                74.0        70.0         0.0       -4.0
Te2/5        31.4                74.0        70.0         0.0       -4.0
Te2/6        30.8                74.0        70.0         0.0       -4.0

                            High Alarm  High Warn  Low Warn   Low Alarm
            Voltage            Threshold   Threshold  Threshold  Threshold
Port        (Volts)            (Volts)     (Volts)    (Volts)    (Volts)
----------  ---------------    ----------  ---------  ---------  ---------
Te1/1       0.00                   N/A         N/A         N/A        N/A
Te1/2       0.00                   N/A         N/A         N/A        N/A
Te1/5       0.00                   N/A         N/A         N/A        N/A
Te1/6       0.00                   N/A         N/A         N/A        N/A
Te2/1       0.00                   N/A         N/A         N/A        N/A
Te2/2       0.00                   N/A         N/A         N/A        N/A
Te2/5       0.00                   N/A         N/A         N/A        N/A
Te2/6       0.00                   N/A         N/A         N/A        N/A

                            High Alarm  High Warn  Low Warn   Low Alarm
            Current            Threshold   Threshold  Threshold  Threshold
Port        (milliamperes)     (mA)        (mA)       (mA)       (mA)
----------  -----------------  ----------  ---------  ---------  ---------
Te1/1         8.0         --     N/A        N/A        N/A       N/A
Te1/2        41.5         --     N/A        N/A        N/A       N/A
Te1/5         7.7         --     N/A        N/A        N/A       N/A
Te1/6         7.7         --     N/A        N/A        N/A       N/A
Te2/1         7.8         --     N/A        N/A        N/A       N/A
Te2/2        42.0         --     N/A        N/A        N/A       N/A
Te2/5         7.5         --     N/A        N/A        N/A       N/A
Te2/6         7.8         --     N/A        N/A        N/A       N/A

            Optical            High Alarm  High Warn  Low Warn   Low Alarm
            Transmit Power     Threshold   Threshold  Threshold  Threshold
Port        (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
----------  -----------------  ----------  ---------  ---------  ---------
Te1/1        -2.0                 2.9        -1.0        -7.3      -11.3
Te1/2        -1.4                 4.4         0.4        -8.2      -12.2
Te1/5        -2.6                 2.9        -1.0        -7.3      -11.3
Te1/6        -2.0                 2.9        -1.0        -7.3      -11.3
Te2/1        -2.6                 2.9        -1.0        -7.3      -11.3
Te2/2        -1.5                 4.4         0.4        -8.2      -12.2
Te2/5        -2.5                 2.9        -1.0        -7.3      -11.3
Te2/6        -2.9                 2.9        -1.0        -7.3      -11.3

            Optical            High Alarm  High Warn  Low Warn   Low Alarm
            Receive Power      Threshold   Threshold  Threshold  Threshold
Port        (dBm)              (dBm)       (dBm)      (dBm)      (dBm)
----------  -----------------  ----------  ---------  ---------  ---------
Te1/1        -2.1                 2.9        -1.0        -9.9      -13.9
Te1/2        -3.0                 4.4         0.4       -14.4      -18.4
Te1/5        -2.8                 2.9        -1.0        -9.9      -13.9
Te1/6        -2.8                 2.9        -1.0        -9.9      -13.9
Te2/1        -1.9                 2.9        -1.0        -9.9      -13.9
Te2/2        -3.5                 4.4         0.4       -14.4      -18.4
Te2/5        -2.8                 2.9        -1.0        -9.9      -13.9
Te2/6        -2.7                 2.9        -1.0        -9.9      -13.9
  
Another nice feature is the timestamp logging of violations:

6509-1#show interfaces transceiver threshold violations
Rx: Receive, Tx: Transmit.
DDDD: days, HH: hours, MM: minutes, SS: seconds

                        Time since Last Known
           Time in slot    Threshold Violation     Type(s) of Last Known
Port       (DDDD:HH:MM:SS)  (DDDD:HH:MM:SS)        Threshold Violation(s)
---------- --------------- ----------------------  ----------------------
Te1/1       0025:05:22:30    0013:22:56:43         Rx power low warning
                                                -12.8 dBm <  -9.9 dBm
Te1/2       0025:05:22:29    Not applicable        Not applicable
Te1/5       0025:05:22:28    Not applicable        Not applicable
Te1/6       0019:20:49:37    Not applicable        Not applicable
Te2/1       0025:05:22:15    Not applicable        Not applicable
Te2/2       0025:05:22:15    Not applicable        Not applicable
Te2/5       0025:05:22:14    Not applicable        Not applicable
Te2/6       0019:20:57:07    Not applicable        Not applicable



The ASR 1000 commands are slightly different, since it's SPA based:


ASR1004-13# show hw-module subslot 0/0 transceiver 3 status
The Transceiver in slot 0 subslot 0 port 3 is enabled.
  Module temperature                        = +35.195 C
  Transceiver Tx supply voltage             = 3299.2 uVolts
  Transceiver Tx bias current               = 21544 uAmps
  Transceiver Tx power                      = -5 dBm
  Transceiver Rx optical power              = -4 dBm


Here is a list of DoM supported optics:

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