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Comments (6)

1 DerekKeightley commented Permalink

Great post Chris, good to know about the netcd daemon, I have previously used open source options.

2 nmistryLH commented Permalink

I have some AIX and DNS related questions based on some recent troubles with a system. We have a p570 with AIX 5.3 that runs oracle 11g. Recently there were some communication issues between DB and App server and it was pointed out it had something to do with DNS. My question is how does AIX handle DNS requests? Does it automatically fail to secondary if primary is not available? Does it go back to primary automatically when its back online? Can we point to more than two DNS servers? <div>&nbsp;</div> Thanks

3 cggibbo commented Permalink

Hi nmistryLH, <div>&nbsp;</div> FYI. <div>&nbsp;</div> There are new options for /etc/resolv.conf in AIX 7.1/6.1 (not in 5.3): <div>&nbsp;</div> timeout: <br /> Enables you to specify the initial timeout for a query to a nameserver. The default value is five seconds. The maximum value is 30 seconds. For the second and successive rounds of queries, the resolver doubles the initial timeout and is divided by the number of nameservers in the resolv.conf file. <div>&nbsp;</div> attempts: <br /> Enables you to specify how many queries the resolver should send to each nameserver in the resolv.conf file before it stops execution. The default value is 2. The maximum value is 5. <div>&nbsp;</div> rotate: <br /> Enables the resolver to use all the nameservers in the resolv.conf file, not just the first one. <div>&nbsp;</div> The resolv.conf file can contain a maximum of three nameserver entries, and any number of options entries. <div>&nbsp;</div> HTH. <div>&nbsp;</div> Chris

4 JMRoderick commented Permalink

Chris, <div>&nbsp;</div> There's some debate here about the use of domain when search is specified, e.g <div>&nbsp;</div> domain biz.co.uk <br /> nameserver <br /> nameserver <br /> nameserver <br /> search biz.co.uk shop.biz.co.uk <div>&nbsp;</div> Documentation says domain and search are mutually exclusive and the last entry wins out BUT it's not completely clear on whether domain can be left out if search is populated (as above). <div>&nbsp;</div> What do you think?

5 cggibbo commented Permalink

"...under DNS 4.9 or DNS 8, you can replace domain nsr.hp.com with search nsr.hp.com hp.com and get the same functionality." <div>&nbsp;</div> http://www.diablotin.com/librairie/networking/dnsbind/ch06_01.htm <br />

6 Mrtyldrm commented Permalink

Hi Chris, <br /> If I lose all of my dns servers which specified on /etc/resolv.conf , Can I reach to a host which it's dns definitions has already on the cache before lost the dns servers. <div>&nbsp;</div> I start the netcd and ping serverA. Check the caching out and see its definitions on there. After remove all dns servers from /etc/resolv.conf and try to ping serverA again but it failed with "host not found message." So can we say the dns caching is useful only when dns servers is up? If no, there is a caching dns option for if all dns servers down

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