Cisco Cisco Email Security Appliance C190 Guía Del Usuario
40-20
User Guide for AsyncOS 9.7 for Cisco Email Security Appliances
Chapter 40 Testing and Troubleshooting
Troubleshooting the Network
•
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
Table 40-3
Checking DNS Functionality: Query Types
Query Type
Description
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
information
SOA
the domain's “start-of-authority” information
TXT
the text information