This article contains frequently asked questions (FAQ) regarding MacDNS, with answers to those questions.

Questions answered in this article:

1. I need a "parent" server, why bother running MacDNS at all? Why not just use my ISP's name server?
2. I work for a large company/university with thousands of computers on the Net. Can I use MacDNS as my primary DNS server? Is MacDNS only for small and medium-sized LANs? What are its limits?
3. How should I configure MacTCP (or Open Transport) on the computer running MacDNS?
4. Can you quickly walk me through the process of setting up MacDNS to serve my domain? My domain name is "intercloud.com" and I am going to be running all my services (mail server, Web server, DNS server) on one computer.
5. Is it possible to specify more than one secondary name server for a given domain?
6. My secondary DNS provider wants the serial numbers for my domain data to be in "YYMMDDnn" format. Does MacDNS support this?
7. How do I serve multiple domains with MacDNS? I want to map "www.intercloud.com" and "www.tyrell.org" to my Web server.
8. How do I set up multiple default home pages on my Web server using MacDNS?
9. How do I set up a default MX record for my domain?
10. How do I set up a wildcard PTR entry for a block of addresses?
11. What can I do to speed up performance of MacDNS?
12. Why do I sometimes see incoming requests in the log file with my local domain name tacked on the end? (i.e. "www.apple.com.mydomain.com")
13. How can I add a new hardware/software type for a host? I have a bunch of PCs, but that isn't one of the hardware options.
14. How can I get rid of the dialog box that asks "Are you sure you want to quit MacDNS?"
15. I'm setting up MacDNS to serve an intranet at my office. Our network isn't connected to the Internet. Should I just make up arbitrary IP addresses for the hosts in my domain?

Question 1: I need a "parent" server, why bother running MacDNS at all? Why not just use my ISP's name server?

Answer : One clear advantage of running MacDNS is that it reduces the amount of outward-bound network traffic on your local-area network (LAN). Lookups for a given host name can be serviced very quickly from MacDNS's cache. Another advantage is that you have control of your domains, instead of your ISP having control. For example, you can add or remove hosts instantly, instead of waiting for a service provider to accomodate your request.

Question 2 : I work for a large company/university with thousands of computers on the Net. Can I use MacDNS as my primary DNS server? Is MacDNS only for small and medium-sized LANs? What are its limits?

Answer : The number of hosts that MacDNS can support is limited only by the amount of memory available to the application.

While it is possible to serve an organization of any size with MacDNS, it is not currently possible to delegate subdomains to another name server. This means that you need to include all hosts from all the subdomains of your domain in the local database. For example, if you serve "domain.com," you would need to include "host1.subdomain.domain.com." and so forth. This requirement might be a nuisance for large sites that have many sub- domains in different locations. In such a situation, you may want to use a centralized, UNIX-based DNS server for the top-level domain, and MacDNS servers for individual subdomains.

Question 3 : How should I configure MacTCP (or Open Transport) on the computer running MacDNS?

Answer : In general, you always want to enter the IP address of the computer that is running MacDNS in the "Domain Name Server Information" area of the MacTCP control panel. You can specify your computer's own IP address as the DNS server to use. This allows other services that may be running concurrently (such as WebSTAR or AIMS) to take advantage of MacDNS's caching, rather than generating outbound network requests.

If you are running Open Transport networking software, enter the IP address of the computer running MacDNS in the "Name server addr" area of the TCP/IP control panel.

Important: Do not specify your own IP address as a parent server in the MacDNS "Set Parent Servers..." dialog box! If you do, it's possible for requests to loop endlessly without being answered, because MacDNS will be forwarding lookups back to itself. (Note: this applies only to MacDNS 1.0. Later versions prevent this situation from occurring.)

Question 4 : Can you quickly walk me through the process of setting up MacDNS to serve my domain? My domain name is "intercloud.com" and I am going to be running all my services (mail server, Web server, DNS server) on one computer.

Answer : Here's a checklist of steps to follow (and pitfalls to avoid), using "intercloud.com" as an example. Consult the MacDNS Administrator's Guide for additional information.

1. If you are connected to the Internet (as opposed to an isolated "intranet"), then you need to specify a parent server. Choose "Set Parent Servers..." from the Hosts menu, then type the name and IP address of at least one other DNS server. Usually this will be your ISP's name server, or a DNS server you were using previously.

2. Create a new zone file. The Zone Information dialog box appears.

1. Type your domain name (intercloud.com) in the Domain Name field.

2. Type the host name that you plan to give to your MacDNS computer in the Primary Server field (for example: ns.intercloud.com). The name you enter here must be the computer's canonical or "real" name, not an alias. If you have a secondary name server for your domain, type its name in the Secondary Server field. (See below if you have more than one secondary name server.)

3. Type the administrator's e-mail address in the Administrator field (for example: hostmaster@intercloud.com). Don't forget to add an account for this user on your mail server.

Primary server entry:

Choose "Add Permanent Host" from the Hosts menu. Type the name of your primary server (ns.intercloud.com) in the Host Name field, and enter its IP address in the field below that. Since this computer is also going to act as a mail server and a web server, you will probably want to set up some additional names for this host. For example, type www.intercloud.com, mail.intercloud.com in the Aliases field to create two appropriate alias names for ns.intercloud.com. (See below if you need to create a name outside of the intercloud.com domain that points to this host.)

Domain name entry (with mail exchanger):

Your zone should include a separate host entry for the domain name itself (unless you specified intercloud.com as an alias of ns.intercloud.com in the previous step.) Since you don't have a "real" host named intercloud.com, choose "Add MX-Only Host" to create a new host entry for that name. Type 10 ns.intercloud.com in the Mail Exchangers field. This entry lets other mail servers know that ns.intercloud.com handles mail for the domain intercloud.com with a preference value of 10. Note that you can't specify 10 mail.intercloud.com here, because only the canonical name of a mail server can be used for MX mappings.

4. Save your zone file by choosing "Save As..." from the File menu. That's it!

Question 5 : Is it possible to specify more than one secondary name server for a given domain?

Answer : Only one secondary name server can be entered in the Zone Information dialog, but MacDNS does support multiple secondary NS records. To specify more than one secondary name server, you'll need to edit the zone file manually with a text editor. Look for the line that says:

; Nameserver entries

After this line, you'll notice the secondary name server (NS) entry. If you need more secondary servers, just add additional lines. For example:

• mydomain.com. NS secondary.provider.net.
• mydomain.com. NS another.provider.net.
• mydomain.com. NS third.provider.net.
• mydomain.com. NS fourth.provider.net.

Answer: MacDNS starts the serial number at 1 and increments it by 1 each time the zone file is saved. ("DNS and BIND," published by O'Reilly and Associates, describes this method as one of the good ways to manage serial numbers.) The YYMMDDnn format is not part of the DNS specification.

However, you can satisfy your provider's requirements simply by using a text editor to open and edit your zone file. The serial number is stored as part of the SOA (start of authority) record at the beginning of the file; it's the first number following the administrator's e-mail address. For example, if today is February 5, 1996, and it's the first change to this file today, you would change the number to 96020501. After you make this change, just re-open the zone file in MacDNS and you're set.

Question 7 : How do I serve multiple domains with MacDNS? I want to map "www.intercloud.com" and "www.tyrell.org" to my Web server.

Answer: For each unique top-level domain name you want to serve, choose "New Zone File..." from the File menu and enter the domain name in the Zone Information dialog box. You can have multiple zone files open at once. Even if www.tyrell.org is just intended to be an alias to your Web server at www.intercloud.com, you still need to create a zone file for tyrell.org, because you are serving a host within that namespace. In the Zone Information dialog for tyrell.org, enter the same information that you specified for the intercloud.com zone (with the exception of the Domain Name field, of course.) Add a permanent host entry for www.tyrell.org. You can then assign the IP address of the "real" host computer (www.intercloud.com) to this host.

When you map entries across multiple domains to a single IP address in this way, it's important to be aware of how reverse (PTR) queries for the IP address are handled. Only the canonical domain name for a given IP address is returned. Currently, MacDNS defines the canonical name for an IP address as the first permanent host entry it finds which matches that address. To ensure that MacDNS returns a particular name for a reverse lookup when cross-domain host names are mapped to an IP address, simply create or open the zone file containing that entry first.

Question 8 : How do I set up multiple default home pages on my Web server using MacDNS?

Answer: You don't. Serving up a different default HTML page based on the domain name in a URL is an issue for HTTP server software (or an add-on product which runs on a Web server computer, such as HomeDoor from Open Door Networks).

Question 9 : How do I set up a default MX record for my domain?

Answer: Enter the name of the default mail exchanger in the dialog box for the host whose name is the same as your domain name. (If there isn't one, then you need to create an "MX-only" host.) There's no need to enter explicit MX information for each host in the domain.

For example, if you are setting up MacDNS to serve "mydomain.net.", there are two possibilities:

You have a host computer named "mydomain.net."
Choose "Add Permanent Host..." from the Hosts menu to create a host named "mydomain.net."

None of your host computers is actually named "mydomain.net."
Choose "Add MX-Only Host..." from the Hosts menu to create a host named "mydomain.net."

10 mail.mydomain.net., 20 altmail.mydomain.net.

In this example, a computer named "mail.mydomain.net." is specified as the preferred SMTP mail server for this domain. The numbers 10 and 20 are preference values which indicate the relative priority of the mail exchangers: a lower number means a higher priority. Because "altmail.mydomain.net." has a higher preference value, mail will be routed to it only when the preferred server "mail" is unavailable.

Question 10 : How do I set up a wildcard PTR entry for a block of addresses?

Answer: MacDNS does not currently support wildcard entries. Generally, this would be useful if you are running software (such as the Apple IP Gateway) which assigns IP addresses from a pool. To provide reverse name mapping for these IP addresses, you need to create a permanent host entry with a name for each (for example: "IP-pool-1.mydomain.com", "IP-pool-2.mydomain.com", and so on.)

Question 11 : What can I do to speed up performance of MacDNS?

Answer: "Detailed" and "Microscopic" log messages can cause a noticeable performance hit. For fastest performance, choose "Important" or "Critical" from the pop-up menu at the bottom of the Message Log window, and keep the window closed when you are not actively monitoring the server.

Question 12 : Why do I sometimes see incoming requests in the log file with my local domain name tacked on the end? (i.e. "www.apple.com.mydomain.com")

Answer: This situation usually occurs due to the way your client application and TCP/IP are configured on the client end. If you try to look up a name that isn't terminated with a dot, the client assumes that the name isn't a fully-qualified domain name and appends the default domain name to the end before sending off the request. If your DNS client is using MacTCP, try setting '.' as the default domain name; on the client computer, type a period in the box to the left of where you entered the IP address of the DNS server.

Question 13 : How can I add a new hardware/software type for a host? I have a bunch of PCs, but that isn't one of the hardware options.

Answer: It's possible to add new hardware/software types to the popup menus that appear in the Host Information dialog box. However, you'll need to be familiar with ResEdit. Open the MacDNS server application and edit 'MENU' resources ID=8 and ID=9. Each menu item is in the form [name]#[command-ID]. If you add new items to the menu, be sure to continue the command IDs in sequential order (for example, 3002, 3003, 3004, 3005, and so on.) (Disclaimer: This information is provided for testing purposes only. Apple does not recommend or support this modification. Use ResEdit at your own risk.)

Question 14 : How can I get rid of the dialog box that asks "Are you sure you want to quit MacDNS?"

Answer: Upgrade to the latest version of MacDNS, which no longer displays this dialog.

For users of versions earlier than 1.0.3, it's possible to remove the dialog by opening 'STR ' resource ID=354 with ResEdit. If the string is '1' (the default value), the alert is displayed. To disable the alert, change this string to '0'. (Disclaimer: This information is provided for testing purposes only. Apple does not recommend or support this modification. Use ResEdit at your own risk.)

Question 15 : I'm setting up MacDNS to serve an intranet at my office. Our network isn't connected to the Internet. Should I just make up arbitrary IP addresses for the hosts in my domain?

Answer: By convention, IP addresses that you assign for a private network should fall within the following three blocks of the IP address space:

10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255