Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

In greater detail: local addresses are identified by applying the interface netmask to the interface IP 
address. Both of these are set via the Network > Interfaces page or by the 

interfaceconfig

 command 

(or during system setup). If the address space overlaps, the most specific netmask is used. If a destination 
is local, packets are sent via the appropriate local interface.

If the destination is not local, packets are sent to the default router (set via the Network > Routing page 
or with the 

setgateway

 command). The IP address of the default router is local. The output interface is 

determined by the rule for selecting the output interface for local addresses. For example, AsyncOS 
chooses the most specific IP address and netmask that include the default router's IP address.

The routing table is configured via the Network > Routing page (or via the 

routeconfig

 command). A 

matching entry in the routing table takes precedence over the default route. A more specific route take 
precedence over a less specific route.

Each outbound destination domain has its own outbound queue. Therefore, each domain has a separate 
set of concurrency limits as specified in the Destination Controls table. Further, each unique domain not 
listed specifically in the Destination Controls table uses another set of the “Default” limits as set in the 
table.

Use the Mail Policies > Destination Controls page in the GUI or the 

destconfig

 command in the CLI to 

create, edit, and delete Destination Control entries.

You can configure which version of Internet Protocol addresses to use for the connection to a domain. 
The Email Security appliance uses both Internet Protocol version 4 (IPv4) and Internet Protocol version 
(IPv6). You can configure a listener on the appliance to use one version of the protocol or both.

If the “Required” setting for either IPv4 or IPv6 is specified, the appliance will negotiation a connection 
to the domain using an address of the specified version. If the domain doesn’t use that IP address version, 
no email will be sent. If the “Preferred” setting for either IPv4 or IPv6 is specified, the appliance will 
first attempt to negotiation a connection to the domain using an address of the specified version then fall 
back to the other if the first is not reachable.