Hi all
This is result of tracing www.google.com by dig 9.5.0
; <<>> DiG 9.5.0-P1 <<>> +trace www.google.com
;; global options: printcmd
. 9398 IN NS E.ROOT-SERVERS.NET.
. 9398 IN NS G.ROOT-SERVERS.NET.
. 9398 IN NS K.ROOT-SERVERS.NET.
. 9398 IN NS L.ROOT-SERVERS.NET.
. 9398 IN NS A.ROOT-SERVERS.NET.
. 9398 IN NS J.ROOT-SERVERS.NET.
. 9398 IN NS B.ROOT-SERVERS.NET.
. 9398 IN NS I.ROOT-SERVERS.NET.
. 9398 IN NS D.ROOT-SERVERS.NET.
. 9398 IN NS F.ROOT-SERVERS.NET.
. 9398 IN NS M.ROOT-SERVERS.NET.
. 9398 IN NS C.ROOT-SERVERS.NET.
. 9398 IN NS H.ROOT-SERVERS.NET.
;; Received 272 bytes from 10.10.10.101#53(10.10.10.101) in 0 ms
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
;; Received 492 bytes from 199.7.83.42#53(L.ROOT-SERVERS.NET) in 273 ms
google.com. 172800 IN NS ns1.google.com.
google.com. 172800 IN NS ns2.google.com.
google.com. 172800 IN NS ns3.google.com.
google.com. 172800 IN NS ns4.google.com.
;; Received 168 bytes from 192.41.162.30#53(l.gtld-servers.net) in 296 ms
www.google.com. 604800 IN CNAME www.l.google.com.
l.google.com. 86400 IN NS c.l.google.com.
l.google.com. 86400 IN NS b.l.google.com.
l.google.com. 86400 IN NS a.l.google.com.
l.google.com. 86400 IN NS g.l.google.com.
l.google.com. 86400 IN NS e.l.google.com.
l.google.com. 86400 IN NS d.l.google.com.
l.google.com. 86400 IN NS f.l.google.com.
;; Received 276 bytes from 216.239.34.10#53(ns2.google.com) in 349 ms
Here is result of querying ns record from ns1.google.com
> google.com
Server: [216.239.32.10]
Address: 216.239.32.10
------------
Got answer:
HEADER:
opcode = QUERY, id = 6, rcode = NOERROR
header flags: response, auth. answer, want recursion
questions = 1, answers = 4, authority records = 0, additional = 4
QUESTIONS:
google.com, type = NS, class = IN
ANSWERS:
-> google.com
nameserver = ns2.google.com
ttl = 345600 (4 days)
-> google.com
nameserver = ns3.google.com
ttl = 345600 (4 days)
-> google.com
nameserver = ns1.google.com
ttl = 345600 (4 days)
-> google.com
nameserver = ns4.google.com
ttl = 345600 (4 days)
ADDITIONAL RECORDS:
-> ns1.google.com
internet address = 216.239.32.10
ttl = 345600 (4 days)
-> ns2.google.com
internet address = 216.239.34.10
ttl = 345600 (4 days)
-> ns3.google.com
internet address = 216.239.36.10
ttl = 345600 (4 days)
-> ns4.google.com
internet address = 216.239.38.10
ttl = 345600 (4 days)
------------
google.com
nameserver = ns2.google.com
ttl = 345600 (4 days)
google.com
nameserver = ns3.google.com
ttl = 345600 (4 days)
google.com
nameserver = ns1.google.com
ttl = 345600 (4 days)
google.com
nameserver = ns4.google.com
ttl = 345600 (4 days)
ns1.google.com
internet address = 216.239.32.10
ttl = 345600 (4 days)
ns2.google.com
internet address = 216.239.34.10
ttl = 345600 (4 days)
ns3.google.com
internet address = 216.239.36.10
ttl = 345600 (4 days)
ns4.google.com
internet address = 216.239.38.10
ttl = 345600 (4 days)
>
As shown above ,the first result from dig show that ns1.google.com record in
com. has ttl= 172800 but the second result from querying one of
google.comzone authorize which in is case is
ns1.google.com show that ttl=345600.
If one day google.com remove ns1.google.com from com. or any changing to
ns1.google.com. How fast do other domain 's caching dns know these changing?
172800 or 345600 ?
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