Black Cats Through
Striker Tommy Smith came good at the perfect time to fire Sunderland into the last 16 of the FA Cup.
Smith was forced to wait until Boxing Day for his first goal of the season after signing from Watford in September, but he took his chance at Portman Road with an excellent finish in the absence of suspended Marcus Stewart.
The forward had watched from the sidelines with an ankle injury during Sunderland's third-round victory over Hartlepool, but his goal on the stroke of half-time stung Ipswich, and Julio Arca wrapped up the win after the interval before Ipswich snatched a late consolation.
McCarthy was forced to alter his starting line-up with Stewart banned and on-loan midfielder Kevin Cooper denied permission to play by Wolves.
Paul Thirlwell and Darren Williams came into the side, but the Black Cats looked short of ideas early on without the influence of Stewart up front.
Ipswich also struggled to create chances, and the visitors almost opened the scoring with their first real attack after 13 minutes.
Williams' cross into the box was chested down by Kevin Kyle, and the Scotland international drove a shot on the turn narrowly wide of the post.
John McGreal's off-target volley was a rare opportunity for Ipswich although Sunderland goalkeeper Mart Poom kept his side level with a good save from Jim Magilton with 17 minutes gone.
Tommy Miller also threatened with a long-range shot which deflected off Jeff Whitley before it could trouble Poom, but Kelvin Davis was then forced into a decent block to keep out Smith's strike.
Miller saw another goalbound effort block by Sunderland defender Joachim Bjorklund, and Ian Westlake fired wide from outside the box as Ipswich increased the tempo.
But a disappointing 45 minutes came to life just before half-time when Smith struck for the visitors.
Williams' cross fell to the Sunderland striker, who controlled the ball before driving a clinical shot beyond Davis and into the bottom corner of the net.
Ipswich responded well after the restart with Pablo Counago firing wide from a promising position, but Jason McAteer and Julio Arca both threatened Davis as Sunderland went for the jugular.
And the game was settled in the 68th minute when Arca struck for the third time in three games.
Poom denied Shefki Kuqi with an excellent block, and the Black Cats immediately broke up field before Fabian Wilnis ended the attack by fouling Thirlwell.
McAteer's drove the resulting free-kick straight at Davis in the Ipswich goal, but the keeper spilled the ball and Arca pounced to hammer home the rebound.
Ipswich knew they were beaten but continued to throw players forward, and Royle's side were rewarded when Poom parried Kuqi's strike into the path of Martijn Reuser, who hit the net in the final minute.