There is a problem that the size limit of characters for "DNS name" are too short. Because of it, sometimes we cannot register DNS name even if it is correct.

According to RFC1035, the size limit of characters for DNS name is listed below.

• names: 255 octets or less

In fact, the size limit of characters are limited as 253, because each label has one octet and the end of DNS name has one octet which indicates an empty label.

In spite of it, the length of "DNS name" for Zabbix hosts is limited 64 at most. If we try to assign longer DNS name than 64, the DNS name is regarded as improper name, so we cannot register the DNS name which has more than 64 characters.

Also there is a relative problem that we cannot do name resolution when we try to do it to a DNS name which has exactly 64 characters. The reason is why there are something wrong with processes which add "." to indicate TLD. Normally, when we put "." at the end of DNS names to resolve DNS names. An example is below.

• foo.bar.example.com -> foo.bar.example.com.

However, the 64th character is replaced to "." when we assign 64 characters for DNS names. An example is below.

• aaaaaaaaaabbbbbbbbbbccccccccccddddddddddeeee.foo.bar.example.com -> aaaaaaaaaabbbbbbbbbbccccccccccddddddddddeeee.foo.bar.example.co.

As a result, we cannot do name resolution of DNS names which has 64 characters. So we have to assign less than 63 characters for DNS name to do name resolution correctly. Considering these situations, the current size limits of Zabbix hosts is too short if you follow the rules of RFC1035 as I mentioned above.

We sometimes fail to register monitoring for AWS because of it. For instance, there are DNS names like a following name in AWS.

• {ELB Name}-NNNNNNNNNN.us-east-1.elb.amazonaws.com
  {ELB Name}

  is the name assigned by us but the other is assigned by AWS. The name assigned by AWS occupies 39 so we fail name resolution if we assign more than 25 characters to

  {ELB Name}

  . We think this is a serious problems in that we do our job correctly and strictly. We hope you will resolve this problem as soon as possible.