Cisco Cisco Email Security Appliance C170 Guia Do Utilizador
B-3
Cisco AsyncOS 8.5.5 for Email Security User Guide
Appendix B Assigning Network and IP Addresses
Strategies for Connecting Your Cisco Appliance
IP Addresses, Interfaces, and Routing
When selecting an interface on which to perform a command or function in the GUI or CLI that allows
you to select an interface (for example, upgrading AsyncOS, or configuring DNS, etc.), routing (your
default gateway) will take precedence over your selection.
you to select an interface (for example, upgrading AsyncOS, or configuring DNS, etc.), routing (your
default gateway) will take precedence over your selection.
For example, suppose you have an Cisco appliance with the 3 network interfaces configured, each on a
different network segment (assume all /24):
different network segment (assume all /24):
And your Default gateway is 192.19.0.1.
Now, if you perform an AsyncOS upgrade (or other command or function that allows you to select an
interface) and you select the IP that is on data1 (192.19.1.100), you would expect all the TCP traffic to
occur over the data1 ethernet interface. However, what happens is that the traffic will go out of the
interface that is set as your default gateway, in this case Management, but will be stamped with the source
address of the IP on data1.
interface) and you select the IP that is on data1 (192.19.1.100), you would expect all the TCP traffic to
occur over the data1 ethernet interface. However, what happens is that the traffic will go out of the
interface that is set as your default gateway, in this case Management, but will be stamped with the source
address of the IP on data1.
Summary
The Cisco appliance must always be able to identify a unique interface over which a packet will be
delivered. To make this decision, the Cisco appliance uses a combination of the packet’s destination IP
address, and the network and IP address settings of its Ethernet interfaces. The following table
summarizes the preceding examples:
delivered. To make this decision, the Cisco appliance uses a combination of the packet’s destination IP
address, and the network and IP address settings of its Ethernet interfaces. The following table
summarizes the preceding examples:
Strategies for Connecting Your Cisco Appliance
Keep these things in mind when connecting your Cisco appliance:
•
Administrative traffic (CLI, web interface, log delivery) traffic is usually small compared to email
traffic.
traffic.
•
If two Ethernet interfaces are connected to the same network switch, but end up talking to a single
interface on another host downstream, or are connected to a network hub where all data are echoed
to all ports, no advantage is gained by using two interfaces.
interface on another host downstream, or are connected to a network hub where all data are echoed
to all ports, no advantage is gained by using two interfaces.
•
SMTP conversations over an interface operating at 1000Base-T will be slightly faster than ones over
the same interfaces operating at 100Base-T, but only under ideal conditions.
the same interfaces operating at 100Base-T, but only under ideal conditions.
•
There is no point in optimizing connections to your network if there is a bottleneck in some other
part of your delivery network. Bottlenecks most often occur in the connection to the Internet and
further upstream at your connectivity provider.
part of your delivery network. Bottlenecks most often occur in the connection to the Internet and
further upstream at your connectivity provider.
Ethernet
IP
Management
192.19.0.100
data1
192.19.1.100
data2
192.19.2.100
Same Network
Different Network
Same Physical Interface
Allowed
Allowed
Different Physical Interface
Not Allowed
Allowed