Adding a new interface to a Synergy Uplink set....will there be any downtime?`

[power10000]

We have currently 4 "fan out" cables from a single 40Gb interface on our Synergy box and would like to add another 40GB link to it.  (we'll be later removing the fan out cables).  Will adding this cause any disruption in traffic at all?  I figure I add it, wait a few minutes, and then go into VMWare to add the adapter as one to use, but just adding the interface on the HPE side will not cause anything to happen at all.  Am I correct?  Or will I lose connectivity for all the connections for a short bit?

[ChrisLynch]

It would help to better understand how you currently have uplinks configured, which uplink port(s) are assigned and what cable/transceiver type(s) are installed.

Generally speaking, changing uplink port allocation can be disruptive.  For how long and to what degree would be dictated if you have deployed an MLAG configuration, where all uplink ports are part of an LACP aggregate/port-channel, or Active/Standby.  LACP would transition very quickly, and shouldn't cause an outage.  Active/Standby could cause a more disruptive outage as port transition from Standby to Active.