How is the Prophet, peace and blessings be upon him, greeted when visiting his mosque, and is visiting the the Prophet's Mosque obligatory?

Visiting the Messenger's Mosque (peace be upon him) is not obligatory, but traveling to it for prayer is a Sunnah. Upon entering the mosque, pray, then greet the Prophet by saying: "Peace be upon you, O Prophet, and the mercy of Allah and His blessings. And may Allah bestow peace and blessings upon you, your family, and your companions." And send abundant prayers and greetings upon him. Then, greet Abu Bakr and Umar and ask Allah to be pleased with them both. Do not rub yourself against the grave, nor supplicate at it; rather, supplicate to Allah anywhere in the mosque or outside of it. Journeys should not be undertaken with the specific intention of visiting any mosque other than three: Al-Masjid al-Haram, the Messenger's Mosque (peace be upon him), and Al-Masjid al-Aqsa.