National parks from Yosemite to Acadia are closed. | AP Photo The shutdown: How it happens

Shutting down the government is nothing like the slow-motion calamity that is sequestration.

Hundreds of thousands of federal employees will face indefinite furloughs. National parks from Yosemite to Acadia will be closed. And if the spending standoff lasts into late October, veterans’ benefit payments would trickle to a stop.


Unlike this year’s across-the-board spending cuts that rarely lived up to the hype, Americans will notice soon enough that their government services have been disrupted — if not canceled. So, Monday will have been the day to get a last look at the National Zoo’s panda cam.

“It’s a different kettle of fish when you say people aren’t going to show up at all,” said a former Clinton administration official central to planning for the last government shutdown in 1995 and 1996.

( POLITICO's full government shutdown coverage)

Appearing in the White House briefing room Monday just hours before the deadline, President Barack Obama assured Americans that air traffic controllers and federal prison guards would remain on the job. They will also still get their Social Security checks and Medicare help. But it won’t be pretty either, he warned, especially for the federal workers who will be sent home without pay until there’s an agreement on Capitol Hill.

“A shutdown will have a very real economic impact on real people right away,” Obama said.

So how exactly does the U.S. government close its doors?

The official word won’t come from the CNN countdown clock. It came via a guidance memo from White House Office of Management and Budget Director Sylvia Mathews Burwell — shortly before midnight Monday — instructing department heads to begin implementing their specific shutdown contingency plans.

( WATCH: Shutdown: Democrats vs. Republicans)

All federal employees should still show up for work Tuesday, where their managers will distribute the official notices on who is and isn’t essential to daily operations. That’s a tricky enough question — one loaded with both legal ramifications and a good bit of psychological baggage — but essentially boils down to the Cabinet secretaries and a skeleton operations crew who have jobs that involve protection of public safety or government property: think military troops, meat inspectors and border patrol.

The furloughed workers will have until about lunchtime Tuesday to wrap up any last-minute business at their desks: securing files, cancelling meetings, conferences and trips, setting up their ‘out-of-office’ email replies and updating voice mail recordings to say they won’t be back on the job until there’s a budget agreement.

Federal employees are also being told to track news sites for updates on when they can come back to work. And as for any other questions about the strict rules surrounding furloughs? Those can be answered by a handy Office of Personnel Management guidance document that describes frequently asked questions like prohibitions on voluntary government work and moonlighting.

( WATCH: Boehner 'confident' House will pass CR)

Some of the largest furloughs will hit the Pentagon and 400,000 of its civilian workers. Defense Secretary Chuck Hagel fretted Monday about how these workers have been among those hit hard by sequestration — with a summer full of unpaid furlough days. Still, he said decisions to send them home without pay “are dictated solely by the law” for protecting people and property.

“The furloughs are in no way a reflection of the importance of your work, the hard effort you put forth every day, or your dedicated service to our department and our nation,” Hagel said in a memo to Defense Department employees while traveling in South Korea.

As for the uniformed troops, they too must report to work, though they’ll have the benefit of receiving their pay thanks to a rare legislative agreement between the House and Senate.

( PHOTOS: 17 times the government has shut down)

The news isn’t so good for veterans. Benefit checks from the Department of Veterans Affairs, including disability claim checks and pension payments, are expected to last only two or three weeks beyond the start of the shutdown. Assistance for veteran-run businesses also will cease, while rehabilitation and education counseling are likely to be limited.

Some programs and government offices will remain open during the shutdown because they rely on mandatory spending or funding streams outside the annual congressional appropriations process. That’s why it’s full steam ahead for the Obamacare insurance exchanges — which coincidentally go live Tuesday — that are central to the Capitol Hill budget impasse.

It’s also why the U.S. Postal Service and Amtrak will continue operating, along with the Federal Highway Administration, Federal Motor Carrier Safety Administration and some parts of the National Highway Traffic Safety Administration — all of which get funding from the federal fuel tax.

Many others aren’t so lucky.

Obama will have “an extremely lean operation” surrounding him at the White House, press secretary Jay Carney told reporters Monday. Carney couldn’t promise daily news briefings, though he said the president’s trip to Asia planned for next week was still on schedule.

Most Cabinet agencies will be operating at less than full strength too.

Interior Secretary Sally Jewell’s office will have about 550 employees out of 2,855, while some of the non-emergency websites in her department will effectively shut down. Transportation Secretary Anthony Foxx plans to slice his immediate staff in half.

And the State Department will impose a hiring freeze and stop all training except for some courses involving Afghanistan, Iraq and other global hot spots. Non-furloughed employees at Foggy Bottom and dispatched worldwide are also being told to refrain from giving public speeches.

Got a question for Uncle Sam? There’s a good chance it’ll have to wait until the shutdown ends because the Treasury Department and IRS will send home more than 90 percent of their employees. That means no public hotlines or customer service help. And while IRS employees who process electronic tax returns will be on the job, anyone who filed a late 2012 tax return should still count on a delay on refund checks.

Most K-12 schools and higher education should get through the first week of a shutdown without any immediate effects, even though the Education Department does plan to furlough about 90 percent of its 4,225-person workforce. Pell Grants and student loans will still be paid out. So will many of the other federal funding flows under Title I and II, IDEA and career and technical education.

But the longer the shutdown lasts, the higher the chance of big paperwork backlogs and other problems for schools, colleges and students who get federal funding.

Skeleton crews will also be in place at several other key agencies. NASA will keep its Mission Control Center in Houston operating, but much of the rest of the agency plans to close. The National Park Service will keep its firefighting crews in place wherever there’s an active fire and in other areas with high threat levels. And the National Weather Service is holding on to 4,000 employees as the hurricane season enters its final two months.

At EPA, about 1,000 people — mostly enforcement and lab scientists - will remain out of a total workforce of more than 16,000. The Nuclear Regulatory Commission has funding to last about a week. After that, a crew of about 300 will be on duty, including resident inspectors who oversee reactors around the country and the staff who would make up the initial response in the event of a nuclear accident.

If there’s an oil spill, the Bureau of Ocean Energy Management will be in position to respond, though it will shutter much of its other work surrounding leasing, environmental studies and reviews of exploration and production plans.

At the National Institutes of Health, clinical center patients can still expect care. But NIH won’t admit most new patients or process grant applications and awards.

The Centers for Disease Control and Prevention also plans to keep running its 24-hour operations center. Mandatory funding streams will also save its AIDS and vaccination programs. But the Atlanta-based agency will suspend its flu shot program, some outbreak detection monitoring and support to states for infectious disease surveillance.