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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!news.ecn.uoknor.edu!feed1.news.erols.com!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!news.sprintlink.net!news-peer.sprintlink.net!newsfeed.internetmci.com!news.easystreet.com!not-for-mail From: tedm@agora.rdrop.com (Ted Mittelstaedt) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Nslookup and host versus ftp, ping, etc. - strange problem Date: 7 Mar 1997 06:09:52 GMT Organization: Cool Dudes Inc. Lines: 75 Message-ID: <5fobfg$j4g$1@easystreet03> References: <331e3940.135979897@news.diac.com> NNTP-Posting-Host: sunnet.portsoft.com X-Newsreader: WinVN 0.92.6+ Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:36737 In article <331e3940.135979897@news.diac.com>, sitaram@diac.com (Sitaram Chamarty) says: > > >I have a FreeBSD 2.1.6 machine called "sitagw2k" from which "ping >sitagw2k", "ftp sitagw2k", "telnet..." etc work fine. But "host >sitagw2k" and "nslookup sitagw2k" don't work. I dont have "named" >running - we have a gateway/firewall machine which is used as a >nameserver as well as our link to the outside world. That part is >fine: "nslookup ftp.freebsd.org" returns 165.113.58.253 and >wcarchive.cdrom.com, for instance. > >So I have the peculiar situation that these commands can find others, >but not the machine on which they are running! > Not that particular, these commands are querying the nameserver which of course doesen't have an entry for your machine, so it's returning a "host unknown" >Details of configuration: > >This is FreeBSD 2.1.6 on an unused P75 that nobody claimed - it is >*not* possible to sanctify its existence by including its name and IP >address in the NIS maps because if I attempt to do that I might lose >the machine (don't ask :-) So I always refer to it by its IP address, NIS doesen't have anything to do with this. > >But I loaded apache today, and got an unknown host error when >attempting to "http://iii.jjj.kkk.lll/~sitaram" (where the iii stuff >is the IP address). The error I got was that "sitagw2k.mydomain.com" >was not found - it had resolved the IP address into a name, then >failed on the name lookup! > Your running into one of these grey areas. Unfortunately, there is no RFC that covers how a host is supposed to act when BOTH it's HOSTS file and it's nameserver contain valid data. So, it is implementation dependent. In your case, the resolver library is querying the DNS, which is returning an "unknown host" and the resolver is then saying "OK, I'm done so I'll tell the application that the IP number bombed out" This is understandable, because after all the nameserver did respond with a valid response, it's just not the response you want. If the nameserver were offline, or the resolv.conf file was missing, then the resolver library would get an error upon attempting to query a nameserver. It would then fall back to the local hosts file in a last ditch effort to obtain a name-to-IP number mapping. Now, in my opinion, the Right Thing to Do for a properly programmed resolver is that if they get a "host unknown" response from a valid nameserver that it should make a last-ditch effort to look for the number/name in the local HOSTS file. Unfortunately, most programmers apparently don't feel this way because most resolvers out there ignore HOSTS if an active DNS server is present. You have two avenues to fix this: 1) You can run a local copy of named in "caching-only" mode, and make it authorative for your own IP network number. This means that if your admins make a change in the DNS for your own network, you won't see it unless you make the same change in your own DNS database. It will work for outside hosts, just not your own domain. (unless you have entered hosts in it) This may or may not be a problem for you. You then (obviously) create a resolv.conf pointing to your own machine. 2) You can modify the source for libresolv so that it falls back to your own HOSTS file no matter what before returning with a host unknown, then recompile everything that uses it. Ted