/etc/resolv.conf issue

[Javed Khan_1]

Hi All,
I am facing a strange problem with resolver on hp unix .
I have three dns server mentioned in the my resolv.conf

Today i had a problem with my first dns server and it was not reachable.This case my system was unable to resolv ip addresses perhpas it took 5 min time to direct resolver to 2nd dns server .

How can i make resolver to go to second dns server in case first dns server is not available without retrying for first server ..

Thx

[whiteknight]

Javed,

Example:-

# more /etc/resolv.conf
domain mys.xx.com
search mys.xx.com
nameserver 16.110.135.51
nameserver 16.110.135.52


WK
please assign points

[Javed Khan_1]

hello,
what exactly i need is how to reduce timeout between first and second dns server retry .

if first dns server is not available i want my resolver to go to second server immediately without waiting for first dns server to come up.

[AwadheshPandey · Accepted solution]

use retry and retrans
domain xxxx.yy.com
nameserver 164.129.225.119
nameserver 164.129.225.149
nameserver 164.129.225.229
search xxxx.yy.com
retry 3
retrans 300

see man resolv.conf for details

[Javed Khan_1]

I think i found it ..
by setting veriable RES_RETRY=1
so that mean my system will try first dns server for 5 sec then goes to second ..

[Wim Rombauts]

What you face is TCP transmission timeout and has nothing to do with DNS.

Your system sends a request to the DNS server, but since the primary DNS server is dead, the request goes nowhere and the TCP stack keeps waiting for the reply until it times out.
If the DNS-server itself would have been up, while only the DNS service was down, you would get a "connection refused" immediately and fallback immediately to the second DNS server.

The only solution is some clustering functionality that picks-up the IP-address of the DNS server on a second system as sson as the primary DNS system no longer responds. This way the IP-adress remains available and DNS-requests allways get a "connection refused" instead of going nowhere.

[Prasanth V Aravind]

could you check /etc/nsswitch.conf for this

[dirk dierickx]

you could take a look at the 'UNAVAIL' option for the nsswitch.conf file.

it is used as 'NOTFOUND', but this will react when the dns server is unavailable.

check the manpage for resolv.conf for more infos.

[Javed Khan_1]

issue closed by adding retry 1 in /etc/resolv.conf which is quite ok try first dns server for 5 sec , timeout go to second one
Thx for all valuable reply