Rob,
So with SFP/SFP+, transceivers follow a standard outlined in SFF-8472
This standard defines one of the parameters coded in their internal EEPROM which is the transceiver type… such as 1G (SX), 1G (LX), 10G (SR), 10G (LR), etc.
We’ve only found some cheap knockoffs that don’t follow the standard…
In any case, cnMatrix reads the EEPROM when a transceiver is inserted into the SFP cage.
The port speed is configured according to the transceiver type coded in the part.
For cnMatrix switches that have 10G SFP ports, the port speed is default set to 10G. So if a 10G transceiver is plugged in, the port remains at 10G speed.
If a 1G transceiver is plugged in, the port will be automatically configured to 1G speed (from the default 10G)
However, if a transceiver (or DAC) does not have any “transceiver type” coded into the part, the switch will keep the port speed at the current speed setting, as there is no “transceiver type” to guide in the auto speed setting.
For DACs from various vendors, we have found that there are 10G capable cables that either do not have anything coded in the Transceiver Type field, or is coded with a 1000Base-CX type.
As stated above, without a type coding, then the port speed will remain at the previous speed… if it was at 10G, it will remain at 10G speed - and likewise if it was previously set at 1G speed.
For the case of the case of your JD096B-A0 DAC, it is coded as 1000BASE-CX in the type field.
So cnMatrix will auto-set the port speed to 1G, as “instructed” by this transceiver type field.
As Tam mentions, the workaround to this is to manually set the port speed to 10G, for this DAC to run at 10G speed.
Note that manually setting the port speed will override the cnMatrix SFP/SFP+ port speed auto-configure feature.
Thus, if you happen to remove the DAC and replace it with a 1G fiber transceiver (for example), the port speed will remain at 10G, since the manual setting is still in effect.
You would have to re-enable the auto configure of the port in this case…
Hope this explains why cnMatrix is behaving the way it is with the DACs you are using.
Yes, you could mention to the DAC manufacture that their “10G capable DAC” has its transceiver type miscoded as a 1G part (1000Base-CX).