DNS & IP Calculation

The DNS & IP Calculation group gathers the two commands that test name resolution and one address calculator. Verifying which address GTM returns for a name, seeing a TXT record added for certificate validation, or calculating which subnet a VIP falls into is the job of this group.

dig

A detailed DNS query: the record type, the query server, the TTL and the authority information.

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nslookup

Short and fast name or reverse address resolution.

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ipcalc

Network, broadcast address and usable range calculation from an address and a mask.

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Which Command When?

Question	Command	Example
Which address does GTM return for this name?	dig	sys-cmd dig @<gtm-dns-address> app.example.com A +short
Where does the whole chain of name resolution pass through?	dig	sys-cmd dig app.example.com A +trace
Is a name resolved quickly?	nslookup	sys-cmd nslookup app.example.com
What is the reverse record of this IP address?	dig · nslookup	sys-cmd dig -x 10.0.7.20 +short
Which network do this address and mask fall into, and how many addresses are there?	ipcalc	sys-cmd ipcalc 10.20.0.0/22

Common Behavior

Subject	Behavior
Writing	All three are tools with free parameters: everything written after the command name is passed to the tool as it is.
Context	dig and nslookup send the query from within the selected v-device and route table. ipcalc does not send packets to the network; it is not affected by the context.
The query server	If a server is not written, the default resolver on the device is used. In order to make certain which server the result came from, the server is written explicitly: dig @<server>, nslookup <name> <server>.
Pipe	The output can be filtered with | or written to a file with to-file.
Recording	Every run is written to the user logs.

All of the writing rules and the restrictions: System Commands.