North American Network Operators Group|
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical
RE: How common is lack of DNS server diversity?
Regarding "search", I was simply referring to the commonly used dns terminology referring to the "search list". See /etc/resolv.conf on any unix system or "DNS and Bind V3", page 102. Wait a minute, I see where your usage may have originated. W95 network config refers to the nameserver list as "DNS Server Search Order", and to the domain list as the "Domain Suffix Search Order". MS doesn't use this wording in W2k. As far as specifying multiple nameservers (the "nameserver" directive in resolv.conf, or "DNS server addresses" in Win2k), as I said before I tested it and it worked fine in Win2k. Test procedure: Under "Advanced TCP/IP Settings", DNS tab, remove all nameserver addresses, add the address of a non-existent machine, add the address of a working nameserver. Reboot (if you're not doing this with Netswitcher). Test. All services work fine. Nslookup gives you an idea about what is happening under the covers: C:\>nslookup trall2 DNS request timed out. timeout was 2 seconds. *** Can't find server name for address 220.127.116.11: Timed out <- the non-existent nameserver Server: hawk.almaden.ibm.com Address: 18.104.22.168 <- the working nameserver Name: trall2.almaden.ibm.com Address: 22.214.171.124 Nslookup will retry the nameserver list each time, resulting in a resolution delay. But the IP stack resolver remembers which server is working and doesn't retry the bad ones unless needed - there is no resolution delay. Feel free to test this on any other operating system and report your results. Tony Rall Roeland Meyer <email@example.com> on 2001-01-27 11:10:34 To: Tony Rall/Almaden/IBM@IBMUS, Roeland Meyer <firstname.lastname@example.org> cc: email@example.com Subject: RE: How common is lack of DNS server diversity? > From: Tony Rall [mailto:firstname.lastname@example.org] > Sent: Saturday, January 27, 2001 10:54 AM > > >MS DNS, WinNT4 and below, have broken search algorithm > implementations. > >DDNS, Win2K, is currently untested. > > Search algorithm? I thought we were talking about making > full use of the > dns server list - i.e., if first server doesn't respond try > the next one in > the list. I think, *that* is called a search algorithm. Try it at root level, with WinNT, you'll find that it doesn't work. Better yet, try it with BIND8 (*nix, of course) too, and compare the results. If your test doesn't produce the same results, please send test-plan, scripts, and methods to me. I'd be very interested.