This article describes how to configure sample Domain Name Service (DNS) Lookup on NetScaler by using recursive queries.

Recursion refers to the process of having the DNS server itself making queries to other DNS servers on behalf of the client who made the original request. Thereby, the DNS server becomes a DNS client.

If the DNS server does not know the address of the requested site, it forwards the request to another DNS server. To do so, the DNS server must know the IP address of another DNS server that it can forward the request to. Root hint servers provide a list of IP addresses of DNS servers that are considered to be authoritative at the root level of the DNS hierarchy.

On a NetScaler appliance there are 13 root hint servers (default).

If the NetScaler appliance does not have a record for the domain being queried, it forwards the request to one of the root hint servers . If the response is not received from the first root hint server, the appliance sends the request to the second root hint server, and so on until the appliance gets a response.

To configure recursion for DNS resolution on a NetScaler appliance, add the root hint servers to the configuration. These servers are the ones which receive the queries that the NetScaler appliance does not have a record for.

Instructions

To configure recursive DNS, complete the following procedure:

1. Open management GUI and select DNS.
2. Select Change DNS Settings.
   1. Select Enable recursion.
   2. Enable Records caching (Optional).
3. Click OK.
4. Expand the DNS node.
5. Select Name Servers.
6. Click Add.
7. Enter an available IP address on the network.
8. Select Local
9. Click Create.

Run the following commands to configure recursive DNS from the command line interface:

add dns nameserver <IP address> -local

set dns parameter -recursion ENABLED -cacheRecords YES

Important!: The difference between a local DNS server on a NetScaler appliance and an Authoritative Domain Name Service (ADNS) is an ADNS service does not support recursion.