Your ISP automatically assigns DNS servers when your router or computer connects to the internet via DHCP... but you don't have to use those.
Below are free DNS servers you can use instead of the ones assigned, the best and most reliable of which, from the likes of Google and OpenDNS, you can find below:
Free & Public DNS Servers
Provider Primary DNS Server Secondary DNS Server
Level31
209.244.0.3 209.244.0.4
Verisign2
64.6.64.6 64.6.65.6
Google3
8.8.8.8 8.8.4.4
Quad94
9.9.9.9 149.112.112.112
DNS.WATCH5
84.200.69.80 84.200.70.40
Comodo Secure DNS
8.26.56.26 8.20.247.20
OpenDNS Home6
208.67.222.222 208.67.220.220
Norton ConnectSafe7
199.85.126.10 199.85.127.10
GreenTeamDNS8
81.218.119.11 209.88.198.133
SafeDNS9
195.46.39.39 195.46.39.40
OpenNIC10
69.195.152.204 23.94.60.240
SmartViper
208.76.50.50 208.76.51.51
Dyn
216.146.35.35 216.146.36.36
FreeDNS11
37.235.1.174 37.235.1.177
Alternate DNS12
198.101.242.72 23.253.163.53
Yandex.DNS13
77.88.8.8 77.88.8.1
Ùn*énsørédDNS14
91.239.100.100 89.233.43.71
Hurricane Electric15 74.82.42.42
puntCAT16 109.69.8.51
Neustar17
156.154.70.1 156.154.71.1
Below are free DNS servers you can use instead of the ones assigned, the best and most reliable of which, from the likes of Google and OpenDNS, you can find below:
Free & Public DNS Servers
Provider Primary DNS Server Secondary DNS Server
Level31
209.244.0.3 209.244.0.4
Verisign2
64.6.64.6 64.6.65.6
Google3
8.8.8.8 8.8.4.4
Quad94
9.9.9.9 149.112.112.112
DNS.WATCH5
84.200.69.80 84.200.70.40
Comodo Secure DNS
8.26.56.26 8.20.247.20
OpenDNS Home6
208.67.222.222 208.67.220.220
Norton ConnectSafe7
199.85.126.10 199.85.127.10
GreenTeamDNS8
81.218.119.11 209.88.198.133
SafeDNS9
195.46.39.39 195.46.39.40
OpenNIC10
69.195.152.204 23.94.60.240
SmartViper
208.76.50.50 208.76.51.51
Dyn
216.146.35.35 216.146.36.36
FreeDNS11
37.235.1.174 37.235.1.177
Alternate DNS12
198.101.242.72 23.253.163.53
Yandex.DNS13
77.88.8.8 77.88.8.1
Ùn*énsørédDNS14
91.239.100.100 89.233.43.71
Hurricane Electric15 74.82.42.42
puntCAT16 109.69.8.51
Neustar17
156.154.70.1 156.154.71.1