topic Re: Slow Name Resolution in Operating System - HP-UX

Slow Name Resolution

Simon Hargrave — Thu, 12 Dec 2002 10:58:48 GMT

I have recently installed VPO 7.1 on a new server, and am periodically getting the following message generated from NNM: -

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Your Name Services are performing poorly, likely misconfigured. The average for the past 101 lookups took 3846.2 milleseconds, expect less than 500 milleseconds.

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However I have never managed to make it slow, eg interactive nslookup requests come back instantly: -

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perseus:/root# timex nslookup priv_nt_server5
Name Server: ukls04.ukgfls
Address: 172.30.253.3

Trying DNS
Name: priv_nt_server5.ukgfls
Address: 172.28.66.76

real 0.02
user 0.01
sys 0.00

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As far as I can see all my configs are fine: -

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/etc/nsswitch.conf:
hosts: dns [ NOTFOUND=continue TRYAGAIN=continue ] files

/etc/nsswitch.conf:
domain ukgfls
nameserver 172.30.253.3
nameserver 191.254.176.237

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Can anyone suggest what I can do to find out why these error messages are occuring?

TIA

Sy

Re: Slow Name Resolution

U.SivaKumar_2 — Thu, 12 Dec 2002 11:03:34 GMT

Hi,

domain ukgfls
nameserver 172.30.253.3
nameserver 191.254.176.237

Change domain to fully qualified
domain ukgfls.co.uk

Which server has less Round Trip time ?
172.30.253.3 or
191.254.176.237 ?
( Measure the RTT using ping command )
Put the server with lowest RTT as the first nameserver entry in /etc/resolv.conf

regards,
U.SivaKumar

Re: Slow Name Resolution

T G Manikandan — Thu, 12 Dec 2002 11:09:39 GMT

Just discussed before some time

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x2768c1c4ceddd61190050090279cd0f9,00.html

Re: Slow Name Resolution

Simon Hargrave — Thu, 12 Dec 2002 11:10:48 GMT

ukgfls is the fully qualified domain, it's not an external DNS server so only hosts internal domain name structures.

The 172.30 address is on the same subnet, the other DNS server is on another site via ATM link.

The main thing I don't understand though is that my nslookups are as quick as I'd expect, but seemingly NNM is having problems resolving.

Re: Slow Name Resolution

Steven E. Protter — Thu, 12 Dec 2002 15:03:08 GMT

I have noticed that if the DNS server is an external Microsoft server, I get very slow resolution.

Microsoft says its the NIC or HP-UX. HP says its Microsoft not complying with industry standard.

Steve

Re: Slow Name Resolution

Simon Hargrave — Fri, 13 Dec 2002 09:44:48 GMT

Cheers people.

Having run checkDNS I get about 1700 results of the form: -

172.30.253.10 took 4 seconds to resolve
131.12.0.253 took 4 seconds to resolve
172.30.3.253 took 4 seconds to resolve
172.30.4.251 took 4 seconds to resolve
172.30.5.253 took 5 seconds to resolve
...yada yada...

All of these are hosts without DNS entries. Obviously I don't want to add 1700 entries to my hosts file!

Now I presume all these "slow" lookups are impacting on NNMs ability to check all the rest in a timely fashion, so what would you suggest would be the best way to address this?

I think most of the addresses are printers, telephony switches, and virtual interfaces on VLANs etc. I presume I can't make NNM wait less than 4-5 seconds (I presume this timeout would be a global gethostbyname() issue) so is my only option to either unmanage all the addresses, or have the DNS guy add them all?!

Any other suggestions appreciated.

Sy

Re: Slow Name Resolution

Simon Hargrave — Fri, 13 Dec 2002 10:37:11 GMT

Ah, found ipNoLookup.conf. I'll give that a go.