Peter Bissmire
Communications & Language Services
Technical and general translations, French/German -> English
17-09-30
DNS Glue
Many online DNS tests are prone to complaining, incorrectly, that there are "no glue records on the parent server".
What is Glue
Glue is address (A, AAAA) records for your DNS servers. When you register your domain, you should also be asked to nominate DNS servers. This information will be placed on the parent server, along with your domain record. The Glue ensures that the parent server is able to tell a client where to find your DNS records. It avoids the "Where do I go for information about domain x? - Try the name servers for domain x. - Yes- but where are they? - Try domain x." kind of look-up failure loop. It also avoids reversion to the root servers to start resolution of the server names when they lie outside your domain.
What do the "missing Glue" messages mean?
In most cases, this probably means that the test expects to find your name servers within your domain. Most of we lesser mortals do not have a number of IP addresses on which we could run DNS servers. We make use of one or more DNS hosting services, which are probably more reliable anyway. This means that the DNS servers are outside our domain and must be resolvable to addresses if they are to be of any use. Primary responsibility for the Glue lies with the hosting organisation. If your domain registrar permits the entry of both names and addresses for the DNS servers, you can use a subterfuge to provide missing glue yourself - you pretend that the servers are in your domain by giving them false names and enter their real addresses.
If you use ISC BIND (the "standard" DNS server), you will also have the dig resolver. Using a "dig +trace" command for your domain (without host prefixes like www.), you can watch a DNS lookup in action, stage by stage, in slow motion. An initial, very quick response lists the root servers from the local server's hint zone file. There will follow a list of top level domain servers. Next might be a list of regional or country domain servers. Finally, if the glue records are correct, you will see your own or the DNS hoster's servers listed. You can add +additional to the dig command to see both names and addresses.