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Questions and Answers
What is the purpose of Network Address Translation (NAT)?
How does NAT enable Internet access for a large number of users with few public addresses?
What is one benefit of using NAT for migration between ISPs?
How does IP Masquerading work in NAT?
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In NAT, what is the purpose of translating internal private addresses to external public addresses?
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What happens when an organization connects to multiple ISPs without using NAT?
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Why do organizations manage internal private networks in NAT configurations?
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How does NAT handle outgoing connections when selecting an IP address from its pool?
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What role does NAT play in managing a pool of public IP addresses?
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What does NAT do to facilitate migration between ISPs in terms of IP addresses?
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Study Notes
Local Area Network (LAN)
- A set of devices with a common layer 3 gateway
- An Autonomous System (AS) provides Internet connectivity to another group of ASes or end users
Internet Architecture
- Internet is organized in a hierarchical fashion
- Consists of multiple Autonomous Systems (ASes) connected to each other
Autonomous Systems (AS)
- A set of LANs for an administrative domain, identified by a unique AS number
- Routing policies are controlled by a single administrator
IP Addressing
- IP address should identify a network as well as a host inside a network
- Divide the address space (32 bits in IPv4) among network address and host address
Classful Addressing
- Fixed number of bits for network address and host address
- Identified by the first few bits:
- 0: Class A
- 10: Class B
- 110: Class C
- 1110: Class D
- 1111: Class E
Network Address and Broadcast Address
- Network address: identifies a network, all 0's in the host address part
- Broadcast address: sends data to all hosts of a network, all 1's in the host address part
Valid Hosts in a Class
- Class A: 2^24 - 2 = 16,777,214 valid hosts
- Class B: 2^16 - 2 = 65,534 valid hosts
- Class C: 2^8 - 2 = 254 valid hosts
Network Address Translation (NAT)
- Solution to address wastage and reuse
- Translates internal (private) addresses to external (public) addresses
- Hides internal machines from external devices
- Allows Internet access to a large number of users via few public addresses
NAT Operations
- Private address: 10.0.0.0-10.255.255.255, 172.16.0.0-172.32.255.255, 192.168.0.0-192.168.255.255
- Public address: translates internal address to external address
- Basic operation: translates internal address to public address and vice versa
Migration between ISPs
- NAT allows easy interchange between ISPs by changing IP addresses in NAT boxes
- Without NAT, every internal system address needs to be changed to reflect the network IP of the ISP
IP Masquerading
- Single public IP address is mapped to multiple hosts
- NAT box modifies port address and replaces private IP address to public IP address
- Keeps mapping in a table to forward incoming packets to the proper internal host
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Description
Test your knowledge on topics like Local Area Network (LAN), Autonomous System Graph, Internet Service Providers (ISP), Peering between ISPs, and IP Addressing. Get familiar with forwarding data packets between networks and key principles of communication over ISPs.
