Cisco Cisco Email Security Appliance C160 Betriebsanweisung

The number of Virtual Gateway addresses available to you depends on the model of your Cisco IronPort 
appliance. Some appliance models can be upgraded to support more Virtual Gateway addressed via a 
feature key. Contact your Cisco IronPort sales representative for more information about upgrading the 
number of Virtual Gateway addresses on your appliance. 

Cisco has developed a unique Virtual Gateway technology designed to help ensure that corporations can 
reliably communicate with their customers via email. Virtual Gateway technology enables users to 
separate the Cisco IronPort appliance into multiple Virtual Gateway addresses from which to send and 
receive email. Each Virtual Gateway address is given a distinct IP address, hostname and domain, and 
email queue.

Assigning a distinct IP address and hostname to each Virtual Gateway address ensures that email 
delivered through the gateway will be properly identified by the recipient host and prevents critical email 
from being blocked as spam. The Cisco IronPort appliance has the intelligence to give the correct 
hostname in the 

SMTP HELO

 command for each of the Virtual Gateway addresses. This ensures that if a 

receiving Internet Service Provider (ISP) performs a reverse DNS look-up, the Cisco IronPort appliance 
will match the IP address of the email sent through that Virtual Gateway address. This feature is 
extremely valuable, because many ISPs use a reverse DNS lookup to detect unsolicited email. If the IP 
address in the reverse DNS look-up does not match the IP address of the sending host, the ISP may 
assume the sender is illegitimate and will frequently discard the email. The Cisco IronPort Virtual 
Gateway technology ensures that reverse DNS look-ups will always match the sending IP address, 
preventing messages from being blocked accidentally.

Messages in each Virtual Gateway address are also assigned to a separate message queue. If a certain 
recipient host is blocking email from one Virtual Gateway address, messages intended for that host will 
remain in the queue and eventually timeout. But messages intended for the same domain in a different 
Virtual Gateway queue that is not being blocked will be delivered normally. While these queues are 
treated separately for delivery purposes, the system administration, logging and reporting capability still 
provide a holistic view into all Virtual Gateway queues as if they were one.

Before setting up the Cisco IronPort Virtual Gateway addresses, you must allocate a set of IP addresses 
that will be used to send email from. (For more information, see “Assigning Network and IP Addresses” 
in the Cisco IronPort AsyncOS for Email Configuration Guide.) You should also ensure proper 
configuration of your DNS servers so that the IP address resolves to a valid hostname. Proper 
configuration of DNS servers ensures that if the recipient host performs a reverse DNS lookup, it will 
resolve to valid IP/hostname pairs.

After the IP addresses and hostnames have been established, the first step in configuring the Virtual 
Gateway addresses is to create new IP interfaces with the IP/hostname pairs using the Network > IP 
Interfaces page in the GUI or the 

interfaceconfig

 command in the CLI. 

Once the IP interfaces have been configured, you have the option to combine multiple IP interfaces into 
interface groups; these groups can then be assigned to specific Virtual Gateways addresses which the 
system cycles through in a “round robin” fashion when delivering email.