Cisco Cisco Email Security Appliance C370 User Guide

Use the 

nslookup

 command to check the DNS functionality.

The 

nslookup

 command can confirm that the appliance is able to reach and resolve hostnames and 

IP addresses from a working DNS (domain name service) server.

Use the 

tophosts

 command via the CLI or the GUI, and sort by Active Recipients. 

mail3.example.com> nslookup

Please enter the host or IP to resolve.

[]> example.com

Choose the query type:

1. A

2. CNAME

3. MX

4. NS

5. PTR

6. SOA

7. TXT

[1]>

A=192.0.34.166 TTL=2d

A

the host's Internet address

CNAME

the canonical name for an alias

MX

the mail exchanger

NS

the name server for the named zone

PTR

the hostname if the query is an Internet address, otherwise the pointer to other 
information

SOA

the domain's “start-of-authority” information

TXT

the text information