Gerken made a string of superb saves in the second half, while Jack Colback hit the post for Ipswich.
City also rattled the woodwork through Chris Iwelumo, but the game became an exercise in survival for Gary Johnson's men as Town streamed forward but had to settle for their 17th draw of the season.
In the eighth minute Ipswich forward Daryl Murphy broke into the box and teed up his former Sunderland team-mate David Healy. The Northern Ireland striker's effort was spilled by Gerken but City managed to scramble clear.
The visitors did not win their first corner until the 34th minute, but could have taken the lead from the resulting set play when the unmarked Lewin Nyatanga headed wide.
An early pass from Norris 10 minutes before half-time caught City's defence napping and Healy scampered clear only to be thwarted by Gerken, who appeared to handle outside his area in the process but referee Nigel Miller waved away the protests.
Moments later Gerken palmed away a rasping Grant Leadbitter effort before gratefully welcoming Murphy's tame effort from the rebound into his arms.
Iwelumo should have opened the scoring for Bristol City in the 42nd minute when he sprung the Ipswich offside trap to collect Liam Fontaine's lofted ball, but wastefully struck the crossbar with the goal at his mercy.
Ipswich fashioned a good chance a minute after the restart when Murphy got in front of City captain Louis Carey to meet Liam Rosenior's cross, but his stabbed effort with the outside of his left foot ended up over the bar.
The otherwise impressive Bradley Orr trod on the ball in his own penalty area shortly afterwards to present Jonathan Walters with an excellent opportunity but Gerken saved magnificently.
Ipswich came even closer to the elusive goal when Leadbitter slid a piercing through ball to marauding full-back Colback, who was desperately unlucky to see his effort cannon back off the post.
Gerken had to be alert once more in the 56th minute when he pounced on Healy's glancing header from Colback's cross.
At the other end, Ipswich goalkeeper Brian Murphy made a superb save just before the hour after David Clarkson smashed a shot towards goal from the edge of the penalty area.
His namesake Daryl then found himself one on one with Gerken, but the 34-year-old goalkeeper came out on top once again and saw Healy slot the rebound wide.
Gerken's finest moment of the match came in the 70th minute when he blocked Gareth McAuley's thumping header from point-blank range.
Substitute Pablo Counago then latched onto Walter's pass to arc the ball towards the far corner, but Gerken athletically tipped wide.
In stoppage time Ipswich finally had the ball in Gerken's net but Miller correctly ruled that Connor Wickham's long throw had gone straight in.