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Maximum stacking cable length questions

Trusted Contributor

Maximum stacking cable length questions

Mark has some engineering words of wisdom for Virtual Connect and the maximum cable length that should be used between enclosures.


From Mark:




Let me try to clear up this a little. See Below.


Supported cable lengths on 10Gb uplinks are 3 to 15 meters and supported 10Gb stacking links (connecting between two HP Virtual Connect Ethernet Modules) are 0.5 to 7 meters.


Questions from others:


Q1. Is the above statement still correct?

Ans.   Yes this applies to any CX4 connection on a Virtual Connect module, whether it is HP 1/10Gb or 1/10Gb-F or HP Flex-10.


Q2.  If so, why is there a difference between a uplink specification or a  stacking specification?

Ans.  Without going into a in-depth explanation of this, I am going to make a rather general statement and state the reason for this is how the CX4 port configures it Pre-emphasis values. There was much testing around this to ensure that if the port is used as “Stacking Link”, the Pre-emphasis values are automatically configured to optimize and work with cables between .5 meters to 7 meters. If the port is used as a “Uplink”, the expectation is it will be a longer distance, thus we configure the pre-emphasis values to optimize cable lengths of 3-15 meters. So basically there is not 1 set of Pre-emphasis values to cover .5 to 15 meters.  And trying to expose this in a GUI interface doesn’t work, adds confusion. Thus these rules were created and called “Supported configurations”.


Q3.  What is the technical reason for the maximum stacking distance of 7meter?

Ans.    Again, this goes back to optimizing the pre-emphasis values for the CX4 port. And again these rules were setup before we had Multi Enclosure Sstacking (MES).


Q4.  Can you use 10Gb fiber for stacking and if so, what is the maximum length?

Ans.  10Gb Fiber can be any length that matches the specification, in other words, there are no restrictions like with CX4.



I hope this helps in your environments. Have you tried this??