Passport renewal required for H1B petition ?

My employer is filing a h1b petition this year (April 2018) and my passport will expire in Nov 2018. Should i renew the passport before filing the petition?

That’s fine, 6 months validity is a must. So you are good, you may still renew meanwhile and send latest passport if you get it before March 31

What happen if you will not get new passport before 31 march due to any reason?

That’s ok, if you dont get new one. Give old passport scan. But you must get in 15-20 days in general