Jennings, 21, will spend the next month at Edgeley Park to gain first-team experience and free up space in the Iron's budget.
He was signed from Stalybridge last January, but a foot injury kept him out of the team and he has been utilised mostly as a substitute this term.
Brian Laws, the Scunthorpe boss, has targeted an experienced striker as in-form loanee Leon Clarke is unlikely to extend his current spell.
His impressive goal return for the Iron has attracted suitors, and he is likely to be sold by parent club Charlton in the January transfer window. The Addicks also have the option of recalling him with just 24 hours notice.
Ipswich striker Ellington, 31, looks set to be that man - according to reports, initially from their fanzine TWTD.
The former Wigan, West Brom and Watford man is out of favour at the Tractor Boys, and new boss Mick McCarthy is apparently willing to let him leave to play regular first-team football and generate a bit of room in his playing budget.