Chugiak goaltender Joe Lindquist made it possible for Smith to author the clinching goal -- Lindquist stopped 38 shots on a night his team was outshot 40-18 at the McDonald Center.
Defending state champion South also earned a state berth Tuesday night, courtesy of its 5-0 victory over Eagle River at Ben Boeke Arena.
Fifth-seeded Chugiak will face top-seeded Dimond in a CIC semifinal Thursday at Ben Boeke. The Lynx, who went through the CIC regular season 14-0-0, twice beat Chugiak 8-0.
Third-seeded South plays second-seeded Service in Thursday's semifinal at the McDonald Center. The teams split their regular- season meetings, with Service winning 8-2 in November and South winning 5-3 Saturday night.
The semifinalists have all qualified for the state tournament next week in Wasilla. Thursday's CIC semifinals, Friday's consolation match and Saturday's championship game determine the conference's seedings in the state tournament.
Chugiak's Chad Peterson scored 1:56 into the third period to tie East 2-2, and that score held through the remaining 13 minutes of the period and the eight minutes of the first overtime period before Smith ended things.
East's Alex Jackstadt opened the scoring with a first-period, power-play goal and the Thunderbirds raised their lead to 2-0 on Steven Butts' strike midway through the second period.
But the Mustangs countered on Kris Tomazevic's goal with five minutes left in the second period to trim the deficit to 2-1, and Peterson's goal forced extra time.
Chugiak lost its first meeting of the season with East 7-0 and rebounded for a 3-2 win in the regular-season rematch.
South, which outshot Eagle River 33-9, received two goals from Jared Cruz, and goals from Conor Nicoll, Patrick Taylor and Gavin Lubin. Tanner Congdon added two assists and Nathan Wright bagged the shutout.
In three games against Eagle River this season, the Wolverines outscored the Wolves by a combined 14-0.
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