Merge pull request #179660 from asudbring/dns-tb

Edit to paragraph in DNS TB doc

Author: PRMerger14

articles/dns/dns-troubleshoot.md

@@ -59,35 +59,7 @@ DNS name resolution is a multi-step process, which can fail for many reasons. Th
 
 * [Delegate a domain to Azure DNS](dns-domain-delegation.md)
 
-## Unhealthy DNS zones
-
-Configuration errors can cause DNS zones to become unhealthy. The following are scenarios that can lead to this behavior:
-
-* **Unhealthy delegation** - A zone contain *NS* delegation records that help delegate traffic from the primary to the child zones. If any of the *NS* records are present in the parent zone, the DNS server is suppose to mask other records below the delegation, except glue records. However, if the zone contains other records below the delegation, the zone will be marked unhealthy.
-
-    The below table provides scenarios and their corresponding zone health outcomes when a zone contains NS delegation record.
-
-    | Scenario | Zone contains </br>NS delegation record? | Zone contains </br>glue records? | Zone contains other </br>records below the </br>delegation? | Zone health |
-    |----------|-------------------------------------|-----------------------------|--------------------------------------------------|-------------|
-    | 1        | No                                  | -                           | -                                                | Healthy     |
-    | 2        | Yes                                 | Yes                         | No                                               | Healthy     |
-    | 3        | Yes                                 | No                          | No                                               | Healthy     |
-    | 4        | Yes                                 | No                          | Yes                                              | Unhealthy   |
-    | 5        | Yes                                 | Yes                         | Yes                                              | Unhealthy   |
-
-    **Recommendation:** Remove all records except glue records under delegation records in your zones.
-
-* **Zero TTL** - TTL (time to live) is a setting that tells the DNS resolver how long to cache a query before requesting a new one. The information gathered is then stored in the cache of the recursive or local resolver for the TTL duration before it reaches back out to collect new and updated details.
-
-    If the TTL is set to 0 in the configuration, then you can experience one of the following issues:
-
-    * Long response.
-    * Increase in DNS traffic and cost.
-    * Prone to DDoS attacks.
-
-    **Recommendation**: Ensure the TTL value isn't set to *0*. 
-
-## DNS zone status
+## DNS zone status and unhealthy delegation scenarios
 
 DNS zone status indicates the current status of the zone. DNS zone status can be **Unknown**, **Available**, and **Degraded**.