User's Manual

Configuring GRE, NAT, RIPSO, and BFE Services

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308625-14.00 Rev 00

Configuring Dynamic Global Address Ranges

The global address range is a group of registered source addresses used for

address translations. When NAT software detects an outbound packet from an

address within a configured local address range, it maps the local address to a

global address, replaces the packet’s local address with the global address, and

sends the packet to its destination address in another network. When NAT

software detects an inbound packet for a destination address that falls within the

configured global address range, it replaces the packet’s global destination address

with the original local address and sends it to its destination on the local network.

Adding a Global Address Range

The global address range is specified as a base address and a prefix length (from 1

through 32 decimal). The prefix length determines the number of available global

addresses. For example, if the global address range is 197.0.0.0 and its prefix

length is 8 (255.0.0.0), then the address range you specify includes addresses

197.0.0.0 through 197.255.255.255. If the global address range is 197.1.2.0 and its

prefix length is 24 (255.255.255.0), then the address range you specify includes

addresses 197.1.2.0 through 197.1.2.255.

Use the BCC or Site Manager to add global address ranges.

Using the BCC

To configure a global address range, navigate to the global NAT prompt (for

example,

box; ip; nat

) and enter:

global-range

<mask>

address

is the base global IP address expressed in dotted-decimal notation.

mask

is the prefix length associated with the IP address expressed in decimal.

For example, the following command sequence configures 199.1.2.0/24 as the

global address range and verifies the entry:

nat#

global-range 199.1.2.0/24

global-range/199.1.2.0/24#

info

start-address 199.1.2.0

prefix-length 24

state enabled