Overview
This article explains the DNS Request Types that can be collected and listed in a report. Each record type has its own purpose in the DNS infrastructure. When thinking DNS, the first record type that comes to mind is the A Record which is the IPv4 IP address belonging to the hostname of the domain.
Note:
This list is by no means exhaustive. A more complete list, including the relevant RFC for each record type can be found here: https://en.wikipedia.org/wiki/List_of_DNS_record_types
DNS Lookup Types, Descriptions, & Functions
DNS Lookup Type |
Description |
Function |
| A | IPv4 address record |
Returns a 32-bit IP address, which typically maps a domain’s hostname to an IP address, but also used for DNSBLs and storing subnet masks |
| AAAA | IPv6 address record |
Returns a 128-bit IP address that maps a domain’s hostname to an IP address |
| ANY | All cached records |
If the domain is not blocked, Umbrella will return NOTIMP to requests for this record type |
| CNAME | Canonical name record |
Alias of one name to another: the DNS lookup will continue by retrying the lookup with the new name |
| MX | Mail exchange record |
Maps a domain name to a list of message transfer agents for that domain |
| NS | Name server record |
Delegates a DNS zone to use the specified authoritative name servers |
| PTR | Pointer record |
Pointer to a canonical name that returns the name only and is used for implementing reverse DNS lookups |
| SIG | Signature |
Signature record |
| SOA | Start of authority record |
Specifies authoritative information about a DNS zone, including the primary name server, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone |
| SRV | Service locator |
Generalized service location record, used for newer protocols instead of creating protocol-specific records such as MX |
| TXT | Text record |
Carries extra data, sometimes human-readable, most of the time machine-readable such as opportunistic encryption, DomainKeys, DNS-SD, etc. |
Note:
With regards to blocked domains (for security threats, not content filtering), please note that OpenDNS blocks A, AAAA, ANY, CNAME, PTR, SRV, and TXT records (ANY, PTR, and TXT were added as of September 2015), so queries for other record types (MX, NS, and SIG) will be allowed, even though the category is blocked.However, requests for MX records of domains that have been categorized as "DNS Tunneling VPN" will be refused. Also, TXT records will not be blocked by content filtering.