User guide

Summit24e3 Switch Installation and User Guide 111
10 Network Address Translation
(NAT)
This chapter covers the following topics:
• Overview on page 111
• Internet IP Addressing on page 112
• Configuring VLANs for NAT on page 112
• Configuring NAT on page 114
• Displaying NAT Settings on page 117
• Disabling NAT on page 117
Overview
NAT is a feature that allows one set of IP addresses, typically private IP addresses, to be converted to
another set of IP addresses, typically public Internet IP addresses. This conversion is done transparently
by having a NAT device rewrite the source IP address and Layer 4 port of the packets.
Figure 20: NAT Overview
You can configure NAT to conserve IP address space by mapping a large number of inside (private)
addresses to a much smaller number of outside (public) addresses.
In implementing NAT, you must configure at least two separate VLANs involved. One VLAN is
configured as inside, and corresponds to the private IP addresses you would like to translate into other
EW_078
NAT
switch
Outgoing
Incoming
Outgoing
Incoming
Internet
Inside Outside
Private
Network