[TriLUG] Reverse DNS lookup for some local devices is very slow.

[Chris Merrill]

On 9/19/2012 11:49 AM, Aaron Joyner wrote:
> What's your testing methodology?  Are you using nslookup / host / dig
> / ping / something else?

Our software is Java-based running on Windows7, so the lookup happens through the JVM and Windows
network stack.  If I add an entry for the device in question to the windows hosts file, the lookup
in our software is instantaneous, as we would expect.

Running nslookup from Windows responds instantaneously with:
> C:\Users\Chris>nslookup 10.1.1.191
> Server:  drusilla.webperformance.com
> Address:  10.1.1.1
> 
> *** drusilla.webperformance.com can't find 10.1.1.191: Non-existent domain

Our Linux boxes also respond instantly to host, nslookup, ping and dig:
> [build at dev1 build]$ host 10.1.1.191
> Host 191.1.1.10.in-addr.arpa not found: 3(NXDOMAIN)
> [build at dev1 build]$ nslookup 10.1.1.191
> Server:         10.1.1.1
> Address:        10.1.1.1#53
> 
> ** server can't find 191.1.1.10.in-addr.arpa: NXDOMAIN
> 
> [build at dev1 build]$ ping 10.1.1.191
> PING 10.1.1.191 (10.1.1.191) 56(84) bytes of data.
> 64 bytes from 10.1.1.191: icmp_seq=0 ttl=64 time=95.8 ms
> 64 bytes from 10.1.1.191: icmp_seq=1 ttl=64 time=86.1 ms
> 
> --- 10.1.1.191 ping statistics ---
> 2 packets transmitted, 2 received, 0% packet loss, time 1014ms
> rtt min/avg/max/mdev = 86.110/90.972/95.834/4.862 ms, pipe 2
> [build at dev1 build]$ dig 10.1.1.191
> 
> ; <<>> DiG 9.2.4 <<>> 10.1.1.191
> ;; global options:  printcmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19573
> ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
> 
> ;; QUESTION SECTION:
> ;10.1.1.191.                    IN      A
> 
> ;; ANSWER SECTION:
> 10.1.1.191.             0       IN      A       10.1.1.191
> 
> ;; Query time: 3 msec
> ;; SERVER: 10.1.1.1#53(10.1.1.1)
> ;; WHEN: Wed Sep 19 12:53:26 2012
> ;; MSG SIZE  rcvd: 44
> 
> [build at dev1 build]$

Lookups of my droid, however, return a proper name association:
> [build at dev1 build]$ host 10.1.1.109
> 109.1.1.10.in-addr.arpa domain name pointer android-a6423e93xxxxxxxx.webperforma
> nce.com.
> [build at dev1 build]$ nslookup 10.1.1.109
> Server:         10.1.1.1
> Address:        10.1.1.1#53
> 
> 109.1.1.10.in-addr.arpa name = android-a6423e93xxxxxxxx.webperformance.com.

Perhaps the problem is that the local DNS doesn't have a name for the device - so the delay comes
when the lookup falls to an external DNS?  If that is the case, then I guess the question changes to
"Why don't these (IOS/OSX) devices get names on our network?".

TIA!
Chris

-- 
------------------------------------------------------------------------ -
Chris Merrill                           |  Web Performance, Inc.
chris at webperformance.com                |  http://webperformance.com
919-433-1762                            |  919-845-7601

Web Performance: Website Load Testing Software & Services
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