What are three common connectivity problemd (network) ?

Question

and what causes them

Answer 1

I smell a homework question. :)

Backhoes. Especially in springtime, when it's backhoe mating season, and they want to show off their digging prowess and attract potential mates. That, and forgetting to call Miss Utility before you dig. ;)

Fumble-fingered junior network engineers misconfiguring gear.

The third is similar, and another outcome of Murphy's Law...

Answer 2

yo, the 3 most common network connectivity issues. . .are different depending on either mobile users or Desktop users.
but here are some really really common stupid ones..

Ethernet cable unplugged.
Router or Switch is not powered
IP address conficts
wrong domain

here is a good article. .

http://www.pctoday.com/Editorial/article.asp?article=articles/2006/t0404/31t04/31t04.asp

http://support.microsoft.com/kb/325487/