Most nationalities need a visa to visit Egypt and the passport should have at least six months until expiry at the time you enter Egypt.
There are two different types of visa available for travel in the Sinai. One is a 14 day ‘Sinai-only’ visa, issued as a passport stamp at any international Sinai entry point and is free of charge. The 14 day ‘Sinai only’ visa permits travel only on the Sinai’s Gulf of Aqaba coast: Taba, Nuweiba, Dahab and Sharm el Sheikh and St Katherine. All other parts of the Sinai, plus the entirety of mainland Egypt, remain off-limits and you cannot hike the Sinai Trail with it.

The other type of visa is the full Egyptian visa. It costs US$25 and can be purchased at airports or at other points of arrival in Egypt, except from Eilat/Taba border. In this case you must arrange a visa in advance from an Egyptian consulate or online at https://visa2egypt.gov.eg

Offices selling the The Visa are located before the passport control points. Bring $ or any foreigner currency to buy your visa; Egyptian pounds are not accepted. The Visa is valid for 30 days and you can travel anywhere in Egypt. 

Extending a visa in Egypt 
Visas can be renewed at the Visa Office in Sharm el Sheikh. This office is well known to local taxi drivers. Extensions of 6 months are usually issued: to renew, take two  photocopy of the passport ID page, two copy of the visa issued on entry to Egypt and one passport pictures. The Visa is not anymore a stamp in the passport but is a card, like a credit card. It takes two weeks to be ready.