1 © 2004, cisco systems, inc. all rights reserved. scaling ip addresses network address...
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1© 2004, Cisco Systems, Inc. All rights reserved.
Scaling IP AddressesNetwork Address Translation(NAT)
222© 2004, Cisco Systems, Inc. All rights reserved.
Review - Private Addressing
333© 2004, Cisco Systems, Inc. All rights reserved.
NAT (Network Address Translation)
• A NAT-enabled device typically operates at the border of a stub network.
444© 2004, Cisco Systems, Inc. All rights reserved.
NAT Terms
• Inside Local Addresses – An IP address assigned to a host inside a network. This address is likely to be a RFC 1918 private address.
• Inside Global Address – A legitimate IP address assigned by the NIC or service provider that represents one or more inside local IP address to the outside world.
• Outside Local Address - The IP address of an outside host as it known to the hosts in the inside network.
• Outside Global Address - The IP address assigned to a host on the outside network. The owner of the host assigns this address.
555© 2004, Cisco Systems, Inc. All rights reserved.
NAT Features
• Static NAT is designed to allow one-to-one mapping of local and global addresses.
Outside
10.0.0.10 DA
179.9.8.10
Inside
Internet
179.9.8.1010.0.0.10
179.9.8.8010.0.0.2
Inside Global IP Address
Inside Local IP Address
NAT Table10.0.0.2
http://179.9.8.10
DA
10.0.0.10
666© 2004, Cisco Systems, Inc. All rights reserved.
NAT Features
• Dynamic NAT is designed to map a private IP address to a public address.
Outside
10.0.0.10
Inside
Internet
179.9.8.1010.0.0.10
179.9.8.8010.0.0.2
Inside Global IP Address
Inside Local IP Address
NAT Table10.0.0.2
SA
10.0.0.2
SA
179.8.9.80
777© 2004, Cisco Systems, Inc. All rights reserved.
PAT (Port Address Translation) Features
• PAT uses unique source port numbers on the inside global IP address to distinguish between translations.
SA
10.0.0.3:2333
Outside
Inside
Internet
10.0.0.2
SA
10.0.0.2:1456
SA
179.9.8.80:1345
10.0.0.3
179.9.8.80:233310.0.0.3:2333
179.9.8.80:145610.0.0.2:1456
Inside Global IP Address
Inside Local IP Address
NAT Table
126.23.2.2:80126.23.2.2:80
202.6.3.2:80202.6.3.2:80
Outside Global IP Address
Outside Local IP Address
SA
179.9.8.80:2333
202.6.3.2
126.23.2.2
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NAT Benefits
• Eliminates re-assigning each host a new IP address when changing to a new ISP
• Eliminates the need to re-address all hosts that require external access, saving time and money
• Conserves addresses through application port-level multiplexing
• Protects network security
999© 2004, Cisco Systems, Inc. All rights reserved.
Configuring Static NAT Translations
• Static translation are entered directly into the configuration and are permanent in the translation table
Router(config)#ip nat inside source static
10.6.1.20 171.69.68.10
101010© 2004, Cisco Systems, Inc. All rights reserved.
Inside/Outside interface
• An interface on the router can be defined as inside or outside
• Translations occur only from inside to outside interfaces or vice versa—never between the same type of interface
NATInside InterfaceInside
Interface
Inside Network Outside Network
ip nat inside ip nat outsideInside Host Outside Host
Router(config-if)#ip nat inside
Outside InterfaceOutside Interface
111111© 2004, Cisco Systems, Inc. All rights reserved.
Configuring Static NAT
121212© 2004, Cisco Systems, Inc. All rights reserved.
Dynamic Translations
• Dynamic translation specify the pool of global addresses that inside addresses can be translated into
Router(config)#ip nat pool nat-pool
179.9.8.80 179.9.8.95 netmask 255.255.255.240
• Dynamic translations use access lists to identify IP addresses that NAT should create translations for
Router(config)#ip nat inside source list 1 pool nat-pool
Router(config)#access-list 1 permit 10.0.0.0 0.0.255.255
131313© 2004, Cisco Systems, Inc. All rights reserved.
Configuring Dynamic NAT
141414© 2004, Cisco Systems, Inc. All rights reserved.
Configuring PAT
• Establishes overload translation, specifying the IP address to be overloaded as that assigned to an outside interface
Router(config)#ip nat inside source list 1
interface serial0/0 overload
• Establishes overload translation, specifying the IP address to be overloaded as that assigned to a pool name
Router(config)# ip nat pool nat-pool2 179.9.8.20
netmask 255.255.255.240
Router(config)#ip nat inside source list 1
pool nat-pool2 overload
151515© 2004, Cisco Systems, Inc. All rights reserved.
Configuring PAT
161616© 2004, Cisco Systems, Inc. All rights reserved.
Clearing the NAT Translation Table
• Clears all dynamic address translation entries
Router#clear ip nat translation *
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Verifying NAT and PAT Configuration
181818© 2004, Cisco Systems, Inc. All rights reserved.
Troubleshooting NAT and PAT
191919© 2004, Cisco Systems, Inc. All rights reserved.
Issues With NAT
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Summary