MacOS – DNS cache on macOS (Catalina)

dnsmacos

Can somebody share with me a way to display the DNS cache on my MacOS, Catalina (10.15.4)?

Best Answer

It's very likely you don't actually have a DNS cache. If you do, dscacheutil -cachedump seems relevant here, probably sudo dscacheutil -cachedump. That said, I don't see any cache on any system I have, neither server-oriented systems nor end-user laptops.

See man dscacheutil for more.

Denis' answer via the comment will let you see lookups as they happen, but the DNS cache is very short lived if present at all.

Is there an actual problem at hand?

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How long does the DNS cache last in Mac OS X

You can flush the local DNS cache with the following command:

dscacheutil -flushcache

How long a DNS entry is cached typically depends on the TTL of that DNS record, which is configured by the DNS admin of the relevant hostname.

You can find out the (remaining) TTL of any given DNS record with the dig command:

dig apple.stackexchange.com

In the answer section you'll see the remaining TTL right next to the hostname (in this example 257 seconds).

;; ANSWER SECTION:
apple.stackexchange.com. 257    IN  A   198.252.206.16

MacOS – Manually clear dns cache on mavericks

Please check RFC1035, DNS protocol and Understanding the dig command. If the status is SERVFAIL (Server failure. The name server was unable to process this query due to a problem with the name server) you won't get an ANSWER section.

I don't think the problem is on your side.

In 7 attempts querying several name servers i only got one answer:

dig @208.67.220.220 codeship.com
; <<>> DiG 9.8.5-P1 <<>> codeship.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36214
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;codeship.com.          IN  A

;; ANSWER SECTION:
codeship.com.       0   IN  A   54.243.124.75
codeship.com.       0   IN  A   54.225.96.71
codeship.com.       0   IN  A   54.221.223.218

;; Query time: 6126 msec
;; SERVER: 208.67.220.220#53(208.67.220.220)
;; WHEN: Tue Dec 02 02:03:36 CET 2014
;; MSG SIZE  rcvd: 78

Best Answer

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How long does the DNS cache last in Mac OS X

MacOS – Manually clear dns cache on mavericks

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