Richard Brooks wrote:
> Hello Guy
>
> Your just not getting it.
>
> The question is given the ip address of '74.125.127.208', how does one query
> a DNS server (in this case DNS ip 8.8.8.8 = public Google DNS) to get the
> reply 'bskyb-pop3-ssl.l.google.co' (which is the reply Wireshark gets), and
> not the reply 'pz-in-f208.1e100.net', which is what nslookup gets back.
If your system did a DNS lookup of bskyb-pop3-ssl.l.google.com while
Wireshark was running it could have cached the result and used that
resolution.
There is nothing invalid about the PTR record and the A record not
matching. Not good style, but not illegal. The PTR record is in a block
directly allocated to Google. They can map it to whatever they like.
1e100.net have an A record that matches the PTR record. Google have
chosen not to provide PTR records for every A record that might point
into their space. This can be bad news for a mail server.
: dig bskyb-pop3-ssl.l.google.com
; <<>> DiG 9.3.5-P1 <<>> bskyb-pop3-ssl.l.google.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20404
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 0
;; QUESTION SECTION:
;bskyb-pop3-ssl.l.google.com. IN A
;; ANSWER SECTION:
bskyb-pop3-ssl.l.google.com. 300 IN A 74.125.155.208
;; AUTHORITY SECTION:
google.com. 53445 IN NS ns1.google.com.
google.com. 53445 IN NS ns2.google.com.
google.com. 53445 IN NS ns3.google.com.
google.com. 53445 IN NS ns4.google.com.
;; Query time: 209 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Thu Jan 7 22:23:39 2010
;; MSG SIZE rcvd: 133
: dig -x 74.125.155.208
; <<>> DiG 9.3.5-P1 <<>> -x 74.125.155.208
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32369
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 0
;; QUESTION SECTION:
;208.155.125.74.in-addr.arpa. IN PTR
;; ANSWER SECTION:
208.155.125.74.in-addr.arpa. 86400 IN PTR px-in-f208.1e100.net.
;; AUTHORITY SECTION:
125.74.in-addr.arpa. 86190 IN NS NS2.GOOGLE.COM.
125.74.in-addr.arpa. 86190 IN NS NS3.GOOGLE.COM.
125.74.in-addr.arpa. 86190 IN NS NS4.GOOGLE.COM.
125.74.in-addr.arpa. 86190 IN NS NS1.GOOGLE.COM.
;; Query time: 203 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Thu Jan 7 22:26:25 2010
;; MSG SIZE rcvd: 161
: whois 74.125.155.208
OrgName: Google Inc.
OrgID: GOGL
Address: 1600 Amphitheatre Parkway
City: Mountain View
StateProv: CA
PostalCode: 94043
Country: US
NetRange: 74.125.0.0 - 74.125.255.255
CIDR: 74.125.0.0/16
NetName: GOOGLE
NetHandle: NET-74-125-0-0-1
Parent: NET-74-0-0-0-0
NetType: Direct Allocation
NameServer: NS1.GOOGLE.COM
NameServer: NS2.GOOGLE.COM
NameServer: NS3.GOOGLE.COM
NameServer: NS4.GOOGLE.COM
Comment:
RegDate: 2007-03-13
Updated: 2007-05-22
OrgTechHandle: ZG39-ARIN
OrgTechName: Google Inc.
OrgTechPhone: +1-650-318-0200
OrgTechEmail: arin-contact@xxxxxxxxxx
# ARIN WHOIS database, last updated 2010-01-06 20:00
# Enter ? for additional hints on searching ARIN's WHOIS database.
#
# ARIN WHOIS data and services are subject to the Terms of Use
# available at https://www.arin.net/whois_tou.html
: dig px-in-f208.1e100.net.
; <<>> DiG 9.3.5-P1 <<>> px-in-f208.1e100.net.
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36422
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 0
;; QUESTION SECTION:
;px-in-f208.1e100.net. IN A
;; ANSWER SECTION:
px-in-f208.1e100.net. 86400 IN A 74.125.155.208
;; AUTHORITY SECTION:
1e100.net. 172800 IN NS ns4.google.com.
1e100.net. 172800 IN NS ns1.google.com.
1e100.net. 172800 IN NS ns2.google.com.
1e100.net. 172800 IN NS ns3.google.com.
;; Query time: 220 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Thu Jan 7 22:29:39 2010
;; MSG SIZE rcvd: 136
--
There's no point in being grown up if you can't be childish sometimes.
-- Dr. Who
