Final vote: NO
Should probably use something that only allows 1 vote per IP address. I think strawpoll.com and livepoll.io can do that.
VPN voting is also not allowed with this poll. I personally use a VPN and will have to turn mine off to vote on this.
No they shouldn’t, but without any restrictions 1 individual with 300 bot accounts and VPNs can vote as many times as those 300 students.
I doubt a single person would have 300 bots using a single ip address so the measure would be pretty useless anyway. I think restraining votes to a single IP address would not do much good and quite the contrary actually as I see no cases where it would be worthwhile.
Listen: MOST userspace IPs are dynamic, this means that it can change over time, and most likely rebooting the router will do the trick. It’s because amount of IPv4 adresses is very limited.