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The RIPE NCC runs a lameness check once a month on all DNS servers listed as delegation points within the RIPE NCC delegated zones. If a server fails this test, the test will be retried five times over a period of ten days, at varying times of day. If, after ten days, the server continues to fail the test, it is classed as lame.
This chart illustrates the lameness statistics for all servers listed. You can also see DNS lameness statistics with servers sorted per /8.
How Do We Use DNS Lameness Data?
If you are an operator responsible for a server identified as lame, you will receive an e-mail. This will be sent to the address specified RNAME (Responsible Name) field of the Start Of Authority resource record (SOA RR). An e-mail will also be sent to the maintainer listed for the relevant domain object in the RIPE Database.
Definition of Lameness
There are several definitions of "lameness". In the context of these checks, however, a server will only be regarded as lame if it does not satisfy the following criteria:
- The target of a name server resource record (NS RR) must resolve into at least one address record resource record (A or AAAA RR)
- A standard DNS UDP query with RD=0 and with QNAME=<zonename> for an SOA RR in the IN class must result in an authoritative response. This response must originate from the same address the queries were targeted at, and must have a single SOA RR in the QNAME field.
- This testing is network layer protocol independent.
How Can It Be Fixed?
As the operator responsible for a lame server, you will need to correct the zone file for your reverse delegation so that it meets the requirements listed in the definition above.
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