For years the Cambridge City Council has been an easygoing sort of place. A lot of important issues come up--zoning, housing, crime--and every year there's a budget to produce. But, at least since the student protest of the late '60s ended and rent control began to take hold, there's been a feeling that the city is under control.

That confidence vanished suddenly in early November, when Bay State citizens voted 2-1 in favor of a massive cut in local property taxes. Called "Proposition 2 1/2," because it sets a 2 1/2-per-cent limit on the total value of local property that can be collected in taxes, the new law sent a shock wave through city governments across the state.

Hardest hit were big, older cities like Cambridge. The tax collecters here took in $84 million in local property taxes this year; but next fiscal year, as 2 1/2 is phased in, the total will be $12 million less. By the time the law is fully phased in, four years hence, city officials say they will have enough money left to pay Cambridge's share of county and mass transit costs, the interest on its debt, and pensions--but nothing else. No policemen. No firemen. No teachers.

The first layoffs will come in less than a month, when the next fiscal year begins and 2 1/2 officially takes effect. In Cambridge, as many as 500 city workers and 300 teachers will be out of work; and every city program has had its budget slashed 25 per cent. The impending layoffs have, of course, spurred worry and anger; each employee group has jammed into city council chambers to say its piece.

But there seems no way that the city can avoid dramatic cuts, unless the state government massively increases aid to local cities and towns. A flurry of requests and special bills seeking relief has gone to Beacon Hill, where the pleas await the decision of the Democratic leadership and King.

There are preliminary signs that the state will come through with some additional funding; chances are, though, that it will come nowhere near offsetting the impact of 2 1/2 (and the additional cuts that will probably come with the Reagan budget). So the city council will have to vote out a budget, thereby creating a lot of enemies. The lines have already been drawn, with most of the liberals ready to sacrifice a certain number of city jobs to save social programs and most conservatives vowing to keep as many workers on the city payroll as humanly possible.

City manager James Sullivan was one of the first people in the state to realize how devastating 2 1/2 would be to cities and towns and was a leading figure in the unsuccessful statewide drive to defeat the bill. His departure, announced just two weeks ago, will not make the adjustment to 2 1/2 any easier. A veteran of nine years in the city's top administrative post. Sullivan will take over the Greater Boston Chamber of Commerce. Ironically enough, he will leave City Hall the same day 2 1/2 takes effect. "I guess I'll be able to say I never laid anyone off," he said with a weak smile as he announced his resignation.

But Sullivan leaves behind a professional city administration that should be able to cope with the tax cuts. And it will have some trends in its favor. The drop in property tax revenues, for example, will come during the years when Cambridge's tax base should grow at an unprecedented rate. Within the last month city leaders approved blueprints for a major private development in the Lechmere area; similar projects in Harvard Square the Alewife section, and along the route of the Red Line subway extension are also underway.

Other developments have been greeted with less glee by the city fathers, though. The sharpest worries have been over the rapid growth in condominiums, usually by the conversion of scarce rental apartments. In early winter, it seemed the anticondo forces had gained a distinct upper hand, when the State Supreme Court upheld an ordinance effectively barring condominium conversion. Attempts to expand the scope of the law even farther, though, met stiff opposition this spring, and opponents of condo restrictions and rent controls appear to be gearing up for a major offensive in the November city elections.

Harvard's relations with the city remained sour through most of the year; the University drew fire when it finally won its battle to evict tenants from a Sumner Rd. apartment building and received widespread criticism for failing to increase its voluntary payments to the city to help compensate for 2 1/2. The only applause Harvard has won from Cambridge is for its work with neighbors in planning the development of a parcel of land on Mt. Auburn St., cooperation that may become increasingly commonplace with the passage of a tough new law that will allow Cambridge to regulate University expansion.

Paralyzed by 2 1/2, city officials can only look with fright at the future. But there is still pride in a well-managed city and a wonderful history. Cambridge turned 350 in 1980, and more than one person was heard to say that it is likely the city will survive 350 more.