The 26-year-old was cited following an incident during Ireland's victory over Samoa at the Aviva Stadium on Saturday.
Ryan was found guilty of stamping by an independent Six Nations disciplinary committee, chaired by Roger Morris of Wales, and was suspended for three weeks.
The mid-range suspension runs from 15 November until midnight on Sunday 5 December. The suspension means Ryan will miss three Magners League games in total - all against Welsh opposition.
He will miss the game with the Scarlets at Thomond Park, then the trip to Rodney Parade to face Newport Gwent Dragons and then the visit of Cardiff Blues on 4 December.
But the Irish international would be available during the Heineken Cup window before the recommencement of the Magners League on Christmas weekend where Munster travel to Connacht for a Boxing Day clash.
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