On Thu, Apr 08, 2004 at 09:24:58PM +0100, Julien Olivier wrote: > > > > It's there but it doesn't work, at least for me. Whichever hostname I > put in it, I always get the modem provided hostname. Can anyone confirm > that it works for him ? Goodness what a long thread. What most are missing is that the DNS name thing is a way to associate names to IP addresses not to the machine. Another way to think about it is that in IP lan-d the network ports have names not the machines itself. A router can have six or sixty ports each with names that can be looked up via DNS. With DHCP you ask for a valid address on the network you plugged into. The IP-address likely has a name just so they can keep track of it. Long and silly looking names.... Windows mostly ignores DNS and switches to a WINS naming trick. Which works within broadcast domains and with a WINS server. The WINS addresses are often separate and distinct from the IPaddress name space. WINS has a smallish local view of the world. If you fully use DNS in windows land all these issues exist there too. DHCP + DynamicDNS is slightly different. You use DHCP to get an address and pass to the DHCP/DNS server that you want your current leased address to be mapped to such and such a name. For some DHCP+router+RFC-1918 (private address spaces) tangle things further. The router gets an IP address via DHCP. The name of that port is likely a name given to this number by the ISP. It might look like: (adsl-68-22-33-177.dsl.bcvloh.ameritech.net [68.22.33.177]) Now the Linksys (to pick a brand) connects to and authenticates to ameritech.net and requests an IPaddress. It gets 68.22.33.177 back that is in a massive table and has a name "adsl-68-22-33-177.dsl.bcvloh.ameritech.net" so forward and reverse lookups happen. Next the Linksys gets a DHCP requests for one of it's RFC-1918 network numbers. It gets 192.168.1.100... Now things are tangled because DNS service will not have an name for this number and the 192.168.1.xxx network is not routed. Gateway has a public name and address. Other things are hidden behind it. Of interest with /etc/hosts or a local DNS server you can name your RFC-1918 network numbers. You can even setup a dynamic DNS service for them that goes no place because of the nature of RFC-1918 network numbers. There can be interesting effects with multiple IPaddresses. For example by selecting the DNS name of a multi-adapter NFS server you can control to a limited extent which path the bits take into the server. Routers have a thing called host routes that can appear to make all the ports have the same name. When connecting to a public net think about things in stages. First localhost.localdomain and establish a host name as an alias for localhost.localdomain. With that done sendmail can hook up an identity, X can latch to an identity, etc. Next ADD an interface and IP address DHCP, dialup ppp.... what ever. Then there is sendmail... and MX records and.... mail agents... There are some experts out there... have at it some more. -- T o m M i t c h e l l /dev/null the ultimate in secure storage.
