Dave, thanks a million for this clarification. It was enormously helpful. But I'm afraid your answer to my last lingering question was a little unclear, I think because I didn't phrase the question properly :-
Here's the question again ... > Basically, how does a machine on the LAN get resolution to an IP > from a friendly name for a) another machine on the LAN, and b) > a machine somewhere out on the Internet ? You said:- ========= It depends. If the default /etc/host.conf configuration of "hosts, bind" is in effect, then /etc/hosts will be consulted first, then DNS. If the name isn't a FQDN (Fully Qualified Domain Name), and a 'search' directive is in the /etc/resolv.conf file, that will be tacked on if the name doesn't resolve by itself. But in either case, the order of consultation of sources is identical. ========= Your answer is true for the machine hosting hosts. My question should have been:- how does the machine running bind satisfy DNS requests from OTHER machines on local (private) network if it doesn't look at hosts ? Remember that a LAN machine making a DNS request doesn't know yet if the machine whose IP address it wants is on the same network or off in Outer Mongolia. If it's configured to make DNS requests to the local DNS server, shouldn't that local server DNS have a file containing static mappings for it's own DNS authority? Something like a hosts file, in fact? Thanks! Julian. ========================== At 08:42 AM 1/4/02 -0600, you wrote: >On Thu, Jan 03, 2002 at 10:46:25PM -0600, Julian Opificius wrote: > > That much I knew ... it's a data file containing links between IPs and > > friendly names. But who uses it? > >It's used in small networks. It's also used as a "shim" to fix bad DNS >responses. A good example--a friend of mine has DSL service from DirecTV. >I just moved to DirecTV, and found I suddenly can't send mail to him. >Some poking with 'nslookup' and 'dig' showed that one of DirecTV's own >DNS servers is returning a bad IP address for his domain. Until they >figure out what's broken, I've just entered his domain and correct IP >address in my server's local hosts file. Voila! > > > Right, but somebody uses the info in /etc/hosts, don't they? > >Wrong, as I said--it DOES resolve named-to-address, just as does DNS. >The order in which the resolver routines that actually USE lookup services >consult these sources is controlled by /etc/host.conf, which is usually >set to use the local hosts file first. > > > I thought (don't ask me where I got this idea) that bind (ie.named) looked > > in /etc/hosts first before going to an upstream DNS server. > >This is usually true because of the default ordering in /etc/host.conf > > > Don't know what you mean by that. Is the "hosts" file only looked at > > by the machine upon which it resides, then? > >Said elsewhere, but it doesn't hurt to reinforce--yes, this is true. > > > So who is it that looks at /etc/hosts then? > > Help me out here ... > >Do a 'man -k resolv'. Look at all the man pages that are mumbling about >"resolver routines". > > > There's the DNS service, ... > >You have this essentially correct. The only misconception I see--and the >earlier poster also seems to be carrying this--is that the resolver is NOT >the DNS service. The resolver routines USE data sources to determine >address mappings--and these sources are usually only 'hosts' and 'bind'. > >Note that any other name resolution scheme will be consulted, if it's >named in host.conf and honors the resolver interface. > > > Who uses /etc/resolv.conf? Another daemon? > >This file is used by the resolver routines to determine the order in >which DNS servers are consulted when trying to resolve a name. Do >'man 5 resolver'. > > > Basically, how does a machine on the LAN get resolution to an IP > > from a friendly name for a) another machine on the LAN, and b) > > a machine somewhere out on the Internet ? > >It depends. If the default /etc/host.conf configuration of "hosts, >bind" is in effect, then /etc/hosts will be consulted first, then DNS. >If the name isn't a FQDN (Fully Qualified Domain Name), and a 'search' >directive is in the /etc/resolv.conf file, that will be tacked on if >the name doesn't resolve by itself. > >But in either case, the order of consultation of sources is identical. > > > Maybe if you could also tell me where WINS fits into all this, that would > > help a lot too! > >WINS is MicroSoft's own name resolution service. It serves, via different >mechanisms, exactly the same purpose as DNS or hosts--reconcile machine >names to addresses. Its native mode, however, is NETBIOS addressing, >not IP, although there is DNS over WINS. I believe even MicroSoft >is deprecating this as time goes on, but it'll probably never go away >totally. > >Cheers, >-- > Dave Ihnat > [EMAIL PROTECTED] > > > >_______________________________________________ >Redhat-list mailing list >[EMAIL PROTECTED] >https://listman.redhat.com/mailman/listinfo/redhat-list _______________________________________________ Redhat-list mailing list [EMAIL PROTECTED] https://listman.redhat.com/mailman/listinfo/redhat-list
