DNS: Recommended SOA Values
Написал Ярослав Гасов   
03.07.2015

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example.com.  3600  SOA  dns.example.com. hostmaster.example.com. (
1999022301 ; serial YYYYMMDDnn
86400 ; refresh ( 24 hours)
7200 ; retry ( 2 hours)
3600000 ; expire (1000 hours)
172800 ) ; minimum ( 2 days)
Источник: https://www.ripe.net/publications/docs/ripe-203