For example dns setting in one of my server:
;;; begin - dns of 'xl1.mratwork.com' - do not remove/modify this line
$ORIGIN xl1.mratwork.com.
$TTL 86000
xl1.mratwork.com. IN SOA ns1.xl1.mratwork.com. admin.xl1.mratwork.com. ( 2016032704 3600 1800 604800 3600 )
xl1.mratwork.com. IN NS ns1.xl1.mratwork.com.
xl1.mratwork.com. IN NS ns2.xl1.mratwork.com.
cp.xl1.mratwork.com. IN A 104.194.88.110
xl1.mratwork.com. IN A 104.194.88.110
ns1.xl1.mratwork.com. IN A 104.194.88.110
ns2.xl1.mratwork.com. IN A 104.194.88.110
mail.xl1.mratwork.com. IN A 104.194.88.110
www.xl1.mratwork.com. IN CNAME xl1.mratwork.com.
ftp.xl1.mratwork.com. IN A 104.194.88.110
webmail.xl1.mratwork.com. IN A 104.194.88.110
lists.xl1.mratwork.com. IN A 104.194.88.110
smtp.xl1.mratwork.com. IN CNAME mail.xl1.mratwork.com.
pop.xl1.mratwork.com. IN CNAME mail.xl1.mratwork.com.
imap.xl1.mratwork.com. IN CNAME mail.xl1.mratwork.com.
xl1.mratwork.com. IN MX 10 mail.xl1.mratwork.com.
_domainkey.xl1.mratwork.com. IN TXT "t=y; o=-; r=admin@xl1.mratwork.com"
private._domainkey.xl1.mratwork.com. IN TXT ("v=DKIM1; g=*; k=rsa; "
"p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDwtuQMXaGrqZrkkm9GlLKfzVWZ"
"VBXK+j+C5L4/XmLEPEjlnh4NJtJGSD3VDxvwnQOCOV2MU+8jvgEhoBENemHNglg7"
"wYnyiPyKps71mXCQACHJgcn/tI/c5rarW62+MGPz4pqlDjC0HmWSM7Om3jIILANI"
"D14QjGCYNIVe9vesFwIDAQAB")
xl1.mratwork.com. IN TXT "v=spf1 a mx ~all"
_dmarc.xl1.mratwork.com. IN TXT "v=DMARC1; p=quarantine; pct=50; rua=mailto:admin@xl1.mratwork.com"
*.xl1.mratwork.com. IN A 104.194.88.110
;;; end - dns of 'xl1.mratwork.com' - do not remove/modify this line
So, if I want to cloudflare I must copy all settting above to cloudflare and then change 'ns record'. That it.