Hi ,
The reverse is possible(you can make a higher bandwidth capable interface to funtion with lower bandwidth ) but not the other way(40 gig can work as channelised 10 gig ports but not the other way round
You can channelise a higher bandwidth interface to work in multiple sub-interface (40 gig port into 4 channelised 10 gig port.
However remember the below thumb rule:
. "You cannot channelize the 100-Gigabit Ethernet ports when they are operating as 100-Gigabit Ethernet interfaces"
Below two links will explain the above said info in detail:
Please mark my answer as accepted solution, if your query is answered
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