Both sides previously competed in League Two before gaining promotion to League One at the backend of last season and should know what to expect from the other this weekend.
Match preview
Leyton Orient hope home advantage plays in their favour as they seek an encouraging result to avoid the fate that has befallen them far too often in recent years.
The O's have failed to make it out of this stage in five of their last six FA Cup games in the first round proper, a statistic they aim to change on Saturday.
Entering into the competition at this round, Richie Wellens' team could have faced an unfamiliar side from the lower divisions, but they instead do battle with a club not only competing in the same division as them but one they gained promotion with at the backend of last season.
The hosts are the form team heading into the encounter, with a five-game undefeated run before this weekend's game giving fans at Brisbane Road confidence of making it into the second round proper.
Be that as it may, Leyton Orient have recent history at this stage against them and must avoid complacency facing a side they are superior to.
As for Carlisle, the motivation heading into Saturday's game is to put an awful start in League One behind them and end a three-game losing streak against their hosts.
Paul Simpson's men lost both fixtures in League Two last season and have been defeated when both sides faced off in a new division this term, falling to a 1-0 loss on their turf.
Without a goal against the hosts in two of those meetings, ending that scoreless drought against Leyton Orient is imperative to make it into the second round.
History is on Carlisle's side, with progress at this stage secured in eight consecutive seasons since their elimination by Peterborough United in 2014-15.
Despite heading into the game on the back of four defeats in the last five league fixtures, the magic of the FA Cup could be the fillip for Simpson's men to turn the tide.
Leyton Orient form (all competitions):
L
W
W
D
D
D
Carlisle United form (all competitions):
W
L
L
L
W
L
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Team News
Few changes are expected to the Leyton Orient side that drew with Burton Albion last weekend, although Jordan Graham could miss out after going off injured after 13 minutes, while Ed Turns could return to the backline after a one-match suspension.
Ruel Sotiriou was the match-winner when both sides met in mid-October, and the striker could play a pivotal part in Saturday's result.
Carlisle's Alfie McCalmont returned from injury to face Cambridge United, but the midfield man received a straight red in second-half stoppage time, thus ruling him out of this weekend's game.
Jack Robinson could replace the suspended Jack Armer, who also received a red card in the 1-0 loss at Cambridge.
Simpson is expected to stick to the 4-2-3-1 formation utilised in recent games.
Leyton Orient possible starting lineup:
Brynn; Cooper, Happe, Turns; Hunt, Galbraith, Brown, Mizouni, Archibald; Pigott, Sotiriou
Carlisle United possible starting lineup:
Holy; Barclay, Lavelle, Mellish, Robinson; Guy, Moxon; Maguire, Burrerworth, Gibson; Garner