Cisco Cisco Email Security Appliance C170 사용자 가이드

Next, you configure the DNS (Domain Name Service) settings. Cisco IronPort 
AsyncOS contains a high-performance internal DNS resolver/cache that can 
query the Internet’s root servers directly, or the system can use your own DNS 
servers. If you choose to use your own servers, you will need to supply the IP 
address and hostname of each DNS server. You can enter as many DNS servers as 
you need (each server will have a priority of 0.). By default, 

systemsetup

 prompts 

you to enter the addresses for your own DNS servers. 

A “listener” manages inbound email processing services that will be configured 
on a particular IP interface. Listeners only apply to email entering the Cisco 
IronPort appliance — either from your internal systems or from the Internet. 
Cisco IronPort AsyncOS uses listeners to specify criteria that messages must meet 
in order to be accepted and relayed to recipient hosts. You can think of a listener 
as an email listener (or even a “SMTP daemon”) running for IP addresses you 
specified above. 

X1000/1050/1060/1070, C60/600/650/660/670 and C30/300/350/360/370 
customers: By default, the 

systemsetup

 command configures two listeners — 

one public and one private. (For more information on the types of listeners 
available, see 

C10/100/150/160 customers: By default, the 

systemsetup

 command configures 

one public listener for both receiving mail from the Internet and for relaying email 
from your internal network. See 

When you define a listener, you specify the following attributes: 

A name (nickname) created by you to refer to the listener later. For example, 
the listener that accepts email from your internal systems to be delivered to 
the Internet may be called OutboundMail.

One of the IP interfaces (that you created earlier in the 

systemsetup

 

command) on which to receive email.

The name of the machine(s) to which you want to route email (public listeners 
only). (This is the first 

smtproutes

 entry. See “Routing Email for Local 

Domains” in the Cisco IronPort AsyncOS for Email Advanced Configuration 
Guide for more information.)