June 2018
Intermediate to advanced
368 pages
11h 1m
English
Content preview from Managing Mission - Critical Domains and DNS
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SPF
Implementing SPF is a simple matter of enumerating the complete list of hosts that can send or relay for a domain and publishing that list into a TXT RR within the zone:
$ dig +short -t txt example.com "v=spf1 -all"
SPF data fits into the rdata of a TXT RR. It starts with v=spf1 (the current version of the specification) and is composed of mechanisms, where each mechanism is prefixed with a qualifier and optionally modifiers
The available mechanisms are:
- ip4: <address> or <address_range>/<prefix> example: "v=spf1 ip4:192.168.0.1/16 -all"
- ip6: <ip6-network>/<prefix-length> example: "v=spf1 ip6:1080::8:800:200C:417A/96 -all"
- a: <hostname> or <hostname>/<prefix> example: "v=spf1 a:mail.example.com -all"
If <hostname> is omitted, then the ...
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