NAT

1
NAT

• Steve VanDeBogart

2
Outline

• Common NAT m1
• Rewriting based on Port
• Reserved Addresses
• Classic NAT - mn
• Static/Dynamic
• Issues

3
Common Nat m1
Problem?
Solution Private Network
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Reserved Addresses

• 1994 RFC 1597
• Non-Connected Use

• 10.0.0.0 - 10.255.255.255
• 172.16.0.0 - 172.31.255.255
• 196.168.0.0 - 196.168.255.255

• Reserved on I-net?

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Classic NAT mn

• Dynamic Assignment of Real IPs

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Static/Dynamic

• Static
• Assigned once Randomly, or not
• M?N
• Dynamic
• Recycled After last connection closes
• Only N machines can have connections

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Issues

• No Servers
• Protocols with embedded IPs
• FTP
• ICMP
• DNS