On Thu, 2007-12-20 at 23:06 +1100, Simon Slater wrote: > Soooo..., going back to kindergarten..., the names I put in /etc/hosts > were made up to describe the box on a purely internal network. Should > the names/aliases be something different? What would/would not > conflict with public FQDN? Given that intro, I can't resist some fun with domain names... If you have SMTP server running on a machine called bluecrayons (the machine's hostname), then that machine needs to be able to resolve addresses in a way that makes sense to itself at start up. It'll try to resolve the name as the server starts up. It needs to be able to resolve those addresses, to itself, at least. A sample hosts file entry: 192.168.0.1 bluecrayons.example.com bluecrayons mail smtp That's an IP address, a FQDN, and a list of three aliases that you might have used (the hostname, a bog standard "mail" hostname, and another common "smtp" hostname). The latter two aliase being things that some people pick out of habit, but there's nothing saying you must do so, though it does make simple sense to users to configure mail.example.com as their mailserver). Your mail server can start up disconnected from a network, and that's all it'll care about (its own addressing - that out of the interfaces it's using, the addresses resolve). It can start up connected to a network, and the same applies. Thus far, that's all for internal purposes. However, something from outside connecting to your mail server is going to expect a public name to match a public IP address. You could have the same hostname/domain names, and external DNS servers use the external IP address to the machine, and internal DNS servers giving a different IP address to other local machines. e.g. An outside DNS server might associate 208.77.188.166 with bluecrayons.example.com. Outside services would connect to you using that FQDN or IP, and since they both resolve against each other, externally, those outside services are happy about it. As for what won't conflict, don't make use of real domain names belonging to someone else, or make up ones that might be registered by someone at some time. An IP address is how you connect between A and B. A and B might have more than one address. Which one is used depends on the networking. -- (This computer runs FC7, my others run FC4, FC5 & FC6, in case that's important to the thread.) Don't send private replies to my address, the mailbox is ignored. I read messages from the public lists.
