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Chapter 2
Cisco 1710 Security Router Configuration
Configuring Firewalls
Then indicate that any packet received on the inside interface, as permitted by
access list 7, will have its source address translated to an address from the NAT
pool "no-overload."
ip nat inside source list 7 pool no-overload
Alternatively, to handle the case where all inside addresses are translated to a
single outside address, define a NAT pool named "ovrld," which has a range of a
single IP address: 172.16.10.1.
ip nat pool ovrld 172.16.10.1 172.16.10.1 prefix 24
Then indicate that any packet received on the inside interface, as permitted by
access list 7, will have its source address translated to the address from the NAT
pool "ovrld." Translations will be overloaded, which will allow multiple inside
devices to be translated to the same outside IP address.
ip nat inside source list 7 pool ovrld overload
The keyword overload used in this command allows NAT to translate multiple
inside devices to the single address in the pool.
Another variation of this command is
ip nat inside source list 7 interface Ethernet 0 overload, which configures NAT to
overload on the address that is assigned to the Ethernet 0 interface.
Configuring Firewalls
Basic traffic filtering is limited to configured access list implementations that
examine packets at the network layer, or at most, the transport layer, permitting
or denying the passage of each packet through the firewall. However, the use of
inspection rules in Context-based Access Control (CBAC) allows creation and
use of dynamic temporary access lists. These dynamic lists allow temporary
openings in the configured access lists at firewall interfaces. These openings are
created when traffic for a specified user session exits the internal network through
the firewall. The openings allow returning traffic for the specified session (that
would normally be blocked) back through the firewall.
Refer to the Cisco IOS Security Configuration Guide, Release 12.1, for more
detailed information on traffic filtering and firewalls.
Cisco 1710 Security Router Software Configuration Guide
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