{% set nameservers = ["10.1.1.151","10.1.1.152"] %}

{% set nameserver1 = nameservers|random %}
{% set nameserver2 = nameservers|random %}

{% set ns1 = range(0,nameservers|length)|random %}
{% set ns2 = ns1 + 1 %}
{% set ns2 = ns2 % nameservers|length %}

nameserver1: {{ nameservers[ns1] }}
nameserver2: {{ nameservers[ns2] }}