How many DNS servers do you need?!?

[wireless]

My home internet and cell phone both are attached to FOUR DNS servers, that connect automatically on my computer and phone whether I'm at home at work at home or at school 192.168.1.254, 75.153.171.114, 2001:568:ff09:10a::58, 2001:568:ff09:10a::114 are all listed under my DNS connections and if I delete them they just come straight back is this normal? Seems excessive


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