Fibre Channel (SAN)

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Contributor
Posts: 28
Registered: ‎06-21-2011

SFP / cable troubleshooting help

So we have a DCX and a 48000 in our datacenter.

They are linked by 2 ISLs, each is a trunk consisting of two physical connections.

One of the trunks currently has a link down due to a flapping port on the 48000. We have had the SFPs replaced at both ends, one on the 48000 and the corresponding on the DCX.

FYI the ISL is between 10/19 on the 48000 and 1/0 on the DCX.

We have also had the cable replaced (however we are not 100% sure of this). However I am seeing this on an output from sfpshow on both ports:

48000 SAN002 10/19 sfpshow:
                                          Alarm                  Warn
                                      low        high       low         high
Temperature: 23      Centigrade     -25         95         -20         90
Current:     0.206   mAmps          1.000       17.000     2.000       14.000
Voltage:     3249.8  mVolts         2700.0      3900.0     2900.0      3700.0
RX Power:    -2.7    dBm (538.2 uW) 10.0   uW   1259.0 uW  15.8   uW   794.0  uW
TX Power:    -12.8   dBm (52.4  uW) 67.0   uW   631.0  uW  79.0   uW   631.0  uW


DCX  SAN004 1/0 sfpshow:

                                          Alarm                  Warn
                                      low        high       low         high
Temperature: 30      Centigrade     -15         100        -10         95
Current:     6.222   mAmps          2.000       10.500     2.000       10.500
Voltage:     3278.8  mVolts         2800.0      3800.0     2970.0      3630.0
RX Power:    -28.2   dBm (1.5   uW) 0.0    uW   6550.0 uW  49.0   uW   1100.0 uW
TX Power:    -2.4    dBm (573.3 uW) 50.0   uW   800.0  uW  100.0  uW   700.0  uW

Now, it is important to note that the ports are DISABLED at the moment. However I don't understand why TX and RX are OK on one link, but very low values on the other.

Is this default behaviour if the ports are disabled, or is it indicative of one of the cables in the SC cable being faulty?

The link is due to be re-enabled v soon so we need to know if there is a potential problem with this ISL asap!


Regular Contributor
Posts: 164
Registered: ‎05-11-2011

Re: SFP / cable troubleshooting help

Hi William,

you have two directions:

1. 48000->DCX

2. DCX->48000.

In the first direction you send with -12,8 dBm and recieve with -28,2 dBm. So you have attenuation of 15,4 dB.

The second direction you send with -2,4 dBm and recieve with -2,7 dBm. So you have attenuation of 0,3 dB.

Check the cable, check the connectors if they are sitting correct and try to change the cable.

You can also reseat the SFP's on bot sides.

Regards Ralf

Kind Regards
Ralf
Frequent Contributor
Posts: 76
Registered: ‎04-17-2010

Re: SFP / cable troubleshooting help

If the Tx power on SAN002:10/19 is really that low, I would suspect that the transceiver or blade port is bad. Try re-seating that SFP or in case have it replaced.

Note that 'sfpShow' output sometimes doesn't properly update certain fields (subject to FOS release and how you're replacing an SFP, i.e. if you disable the port before pulling it etc.).

Super Contributor
Posts: 635
Registered: ‎04-12-2010

Re: SFP / cable troubleshooting help

sfpshow -f will force an update of the sfp data on newer FOS codes like 6.3.x and newer

Andreas

Super Contributor
Posts: 635
Registered: ‎04-12-2010

Re: SFP / cable troubleshooting help

The RX level on the DCX looks too low and can cause the flapping on 48000.

I would assume that you have a dirty cable because the loss on the line is too high. Do you have the correct cable and SFPs installed?

Andreas

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