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Cisco ASA 5500 Series Configuration Guide using ASDM
OL-20339-01
Chapter 28 Configuring Twice NAT
Configuring Twice NAT
You can also create a new named object or group from the Browse Original Destination Address
dialog box and use this object or group as the real destination address.
Although the main feature of twice NAT is the inclusion of the destination IP address, the destination
address is optional. If you do specify the destination address, you can configure static translation for
that address or just use identity NAT for it. You might want to configure twice NAT without a
destination address to take advantage of some of the other qualities of twice NAT, including the use
of network object groups for real addresses, or manually ordering of rules. For more information,
see the “Main Differences Between Network Object NAT and Twice NAT” section on page 26-15.
Step 4 (Optional) Identify the original packet port (the mapped destination port). For the Match Criteria:
Original Packet > Service, click the browse button and choose an existing TCP or UDP service object
from the Browse Original Service dialog box.
You can also create a new service object from the Browse Original Service dialog box and use this object
as the real destination port.
Dynamic PAT does not support additional port translation. However, because the destination translation
is always static, you can perform port translation for the destination port. A service object can contain
both a source and destination port, but only the destination port is used in this case. If you specify the
source port, it will be ignored. NAT only supports TCP or UDP. When translating a port, be sure the
protocols in the real and mapped service objects are identical (both TCP or both UDP). For identity NAT,
you can use the same service object for both the real and mapped ports. The “not equal” (!=) operator is
not supported.
Step 5 Choose Dynamic PAT (Hide) from the Match Criteria: Translated Packet > Source NAT Type
drop-down list.
This setting only applies to the source address; the destination translation is always static.
Figure 28-13 Setting the NAT Type
Step 6
Identify the translated packet addresses (the mapped source address and the real destination address).
a. For the Match Criteria: Translated Packet > Source Address, click the browse button and choose
an existing network object or interface from the Browse Translated Source Address dialog box.
Figure 28-14 Browse Dialog Box
You can also create a new named object (host) from the Browse Translated Source Address dialog
box and use this object as the mapped source address.
For dynamic PAT, you configure a group of addresses to be mapped to a single address.
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