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Defining Address Pools
Before you can configure dynamic translation, create an address pool. An address
pool is a group of IP addresses from which the NAT router obtains an address when
dynamically creating a new translation. You can create address pools with either a
single range or multiple, nonoverlapping ranges.
When you create a single range, you specify the starting and ending IP addresses
for the range in the root ip nat pool command. However, when you create multiple,
nonoverlapping ranges, you omit the optional starting and ending IP addresses in
the root ip nat pool command; this launches the IP NAT Pool Configuration
(config-ipnat-pool) mode.
The config-ipnat-pool mode uses an address command to specify a range of IP
addresses. You can repeat this command to create multiple, nonoverlapping ranges.
When you create or edit address pools, keep the following in mind:
address
host1(config)#access-list bronze permit ip host any 228.0.0.0 0.0.0.255
Use the no version to delete the access list (by not specifying any other options),
the specified entry in the access list, or the log for the specified access list or
entry (by specifying the log keyword).
See access-list.
Starting and ending IP addresses for the specified range are inclusive and must
reside on the same subnet.
Address ranges are verified against other ranges in the specified pool to exclude
range overlaps. Additional verification occurs when the pool is associated with
a translation rule and the router can determine whether the rule is inside or
outside.
You cannot change the network mask if configured ranges already exist.
The network mask (or prefix length) is used to recognize host addresses that end
in either all zeros or all ones. These addresses are reserved as broadcast addresses
and are not allocated from an address pool, even if they are included in an
address pool range.
You cannot remove an address pool if the pool is part of a translation rule or if
any of the ranges within the pool are still in use. You must issue the clear ip
nat translation command to clear any ranges before you can remove the pool
to which they apply.
Use to specify a range of IP addresses in config-ipnat-pool mode; you can repeat
the address command to create multiple ranges.
Example
host (config-ipnat-pool)#address 171.69.40.110 171.69.40.115
Chapter 2: Configuring NAT
Defining Dynamic Translations
75
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