Paul Howarth: >> Another traditional use was for providing named hosts for each service >> and then providing all services on one host, e.g. >> >> myserver A 10.0.0.1 >> ftp CNAME myserver >> www CNAME myserver >> rsync CNAME myserver >> >> If the load became too high, each service could then be split off onto >> separate machines: Derek Martin: > But this can also be accomplished by using an A record that points to > 10.0.0.1 instead of the CNAME... I think that the usefulness of Paul's example is that you can change the machine acting as "myserver" with one record change (the A record for "myserver". Alternatively, if you made all the next three records "A" records with the same IP address, you'd need to change all of them. Probably not a real pain for three servers, but if you'd faced an annoyance of suddenly having to replace 10, or more, server addresses in one go, you'd probably appreciate being able to fix things with just one modification to one record. >> myserver A 10.0.0.1 >> myserver2 A 10.0.0.2 >> myserver3 A 10.0.0.3 >> ftp CNAME myserver >> www CNAME myserver2 >> rsync CNAME myserver3 >> >> This would all be transparent to people using the "ftp", "www", and >> "rsync" aliases. > Likewise if one is using A records vs. CNAMES here. And it's not > totally transparent... Any changes that are made will screw up > clients that have the old record cached, until the record expires from > the name server's cache -- whether you're using CNAMEs or A records. That's caching, all over. Three really good benefits, and one serious hindrance. Of course, if you hadn't used domain names (harping on about a prior thread), and configured all your clients with IP addresses, you'd have to configure all the other machines when you changed a server. ;-\ -- Don't send private replies to my address, the mailbox is ignored. I read messages from the public lists.
