Alteon Application Switch Operating System Application Guide
Filtering and Traffic Manipulation
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Document
ID:
RDWR-ALOS-V2900_AG1302
13. Check that all SLB parameters are working as expected. If necessary, make any appropriate
configuration changes and then check the information again.
Note:
Changes to filters on a given port do not take effect until the port's session information is
updated (every two minutes or so). To make filter changes take effect immediately, clear the session
binding table for the port (see the
/oper/slb/clear
command in the Alteon Application Switch
Operating System Command Reference).
Network Address Translation
Network Address Translation (NAT) is an Internet standard that enables Alteon to use one set of IP
addresses for internal traffic and a second set of addresses for external traffic. Alteon uses filters to
implement NAT.
NAT serves two main purposes:
•
Provides a type of firewall by hiding internal IP addresses, increasing network security.
•
Enables a company to use more internal IP addresses. Since they are used internally only, there
is no possibility of conflict with public IP addresses used by other companies and organizations.
In the NAT examples in this section, a company has configured its internal network with private IP
addresses. A private network is one that is isolated from the global Internet and is, therefore, free
from the usual restrictions requiring the use of registered, globally unique IP addresses.
With NAT, private networks are not required to remain isolated. Alteon NAT capabilities allow
internal, private network IP addresses to be translated to valid, publicly advertised IP addresses and
back again. NAT can be configured in one of the following two ways:
•
Static NAT provides a method for direct mapping of one predefined IP address (such as a
publicly available IP address) to another (such as a private IP address).
•
Dynamic NAT provides a method for mapping multiple IP addresses (such as a group of internal
clients) to a single IP address (to conserve publicly advertised IP addresses).
Static NAT
In the following example for static NAT (non-proxy), there are two filters: one for the external client-
side port, and one for the internal, server-side port. The client-side filter translates incoming
requests for the publicly advertised server IP address to the server's internal private network
address. The filter for the server-side port reverses the process, translating the server's private
address information to a valid public address.
In
Figure 60 - Static NAT Example, page 385
, clients on the Internet require access to servers on
the private network:
