DNS: Difference between revisions
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*Therefore DNS ALG is used to close the DNS session on getting a reply message.
*If DNS ALG is disabled, the session table may fill in a short time.
; DNS Flow
{{UC}}
= DNS Headers =
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* TC - Truncation Flag
When set to 1, indicates that the message was truncated due to its length being longer than the maximum permitted for the type of transport mechanism used.
TCP doesn't have a length limit for messages, while UDP messages are limited to 512 bytes
So this bit being sent usually is an indication that the message was sent using UDP and was too long to fit.
The client may need to establish a TCP session to get the full message.
On the other hand, if the portion truncated was part of the Additional section, it may choose not to bother.
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Windows Internet Naming Service (WINS)
WINS Reverse Look up (WINSR)
== SOA Record ==
Source: [https://www.cisco.com/c/en/us/support/docs/ip/domain-name-system-dns/12684-dns-resource.html cisco.com]
;SOA Record Data Fields
DOMAIN.NAME
IN
SOA
Hostname.Domain.Name
Mailbox.Domain.Name
Serial number
Refresh
Retry
Expire
TTL
= DNS Record Types =
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IXFR Incremental Zone Transfer Requests a zone transfer of the given zone but only differences from a previous serial number.
<br />
= Authoritative Nameserver = ▼
A recursive resolver would be a DNS server that queries an authoritative nameserver to resolve a domain/
If I have a DNS server in my network that holds an A record for foobar.com, my DNS server would be authoritative for the foobar.com domain.▼
If clients needed to access foobar.com, they could query my DNS server and they would get an authoritative response.▼
= Zone =
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<br />
▲= Authoritative Nameserver =
▲ An authoritative Nameserver is a nameserver (DNS Server) that holds the actual DNS records (A, CNAME, PTR, etc) for a particular domain/ address.
▲ A recursive resolver would be a DNS server that queries an authoritative nameserver to resolve a domain/ address.
▲ If I have a DNS server in my network that holds an A record for foobar.com, my DNS server would be authoritative for the foobar.com domain.
▲ If clients needed to access foobar.com, they could query my DNS server and they would get an authoritative response.
= DNSSEC =
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