Questions and Answers
What is the purpose of NAT (Network Address Translation)?
To conserve IP addresses by allowing many private IPs to share fewer public IPs
Which situation is a key use case for NAT?
What does Static NAT do?
Links one local IP address to one global IP address
Dynamic NAT allows devices in a private network to access the internet using a specific public IP address.
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The ___________ configuration allows multiple devices on a private network to share a single or a small number of public IP addresses for internet access.
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Match the NAT term with its meaning:
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What is the primary function of ICMPv6 in an IPv6 network?
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What is the purpose of NDP in an IPv6 network?
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What command is used to manually assign an IPv6 address to an interface?
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What is the most significant advantage of using IPv6 over IPv4?
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What is the purpose of EUI-64 in IPv6 address assignment?
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What type of IPv6 address is used for communication between devices on the same link?
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What is the result of using the command 'ipv6 address autoconfig' on an interface?
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What is the purpose of OSPFv3 in an IPv6 network?
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What is the purpose of the Router Advertisement (RA) in IPv6 autoconfiguration?
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How do routers handle packets in an IPv6 network?
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What is the destination address of the DHCPv6 Solicit message?
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What is the primary advantage of using dual stack in an IPv6 network?
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What happens when a device on the network does not receive a Router Advertisement (RA) message?
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What is the purpose of the EUI-64 format in IPv6?
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What is the result of padding a MAC address using EUI-64?
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What is the purpose of the Router Solicitation (RS) message in IPv6 autoconfiguration?
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What is the purpose of the Type Field in an ICMPv6 message?
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What is the purpose of the multicast address FF02::2 in IPv6?
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What is the purpose of the default route on the Branch router?
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In OSPFv3, how is the router ID (RID) determined?
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What is the purpose of the Data Field in an ICMPv6 message?
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What is the purpose of the router solicitation (RS) message in IPv6?
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What is the purpose of the OSPFv3 multicast addresses FF02::5 and FF02::6?
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What is the purpose of the static route on the Corp router?
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Study Notes
Network Address Translation (NAT)
- NAT helps conserve IP addresses by allowing many private IPs to share fewer public IPs.
- Key situations for NAT use:
- Internet access without unique IPs
- Changing Internet Service Providers (ISP)
- Merging networks with overlapping IPs
Types of NAT
-
Static NAT (One-to-One Mapping)
- Links one local IP address to one global IP address
- Ideal for situations where each device in your network needs its own unique Internet IP address
- Requires an equal number of public IP addresses as hosts needing direct Internet access
-
Dynamic NAT (Pool Mapping)
- Associates unregistered IP addresses with registered ones from a pool
- Advantages: no need for one-to-one configuration, flexibility in IP address assignment
- Requires enough public IP addresses for all devices that will simultaneously interact with the Internet
-
Overloading (PAT/NAT Overload)
- Allows multiple private IP addresses to share a single public IP address, using different source ports for each session
- Enables thousands of users to access the Internet through a single IP address, significantly conserving IP address space
- Most common use: cost-effective and efficient in utilizing IP addresses
NAT Terms
- Inside Local: The original IP address of an internal device before translation (following RFC 1918 standards)
- Outside Local: The address of the router connected to ISP—the actual Internet address
- Inside Global: The IP address assigned to an internal device after translation, used for Internet communications
- Outside Global: The public IP address of an external destination host
Basic NAT
- NAT translation process:
- Host sends an Internet-bound packet to the border router configured with NAT
- Router identifies the source IP address as an inside local IP address destined for an outside network
- Router translates the source IP address in the packet and documents the translation in the NAT table
- Packet is sent to the outside interface with the new translated source address
- External host returns the packet to the destination host, and the NAT router translates the inside global IP address back to the inside local IP address using the NAT table
Static NAT Configuration
- Command:
ip nat inside source static - Interface configuration for inside network:
interface Ethernet0,ip address,ip nat inside - Interface configuration for outside network:
interface Serial0,ip address,ip nat outside
Dynamic NAT Configuration
- NAT pool creation:
ip nat pool netmask - Interface configuration:
interface Ethernet0,ip address,ip nat inside - Interface configuration:
interface Serial0,ip address,ip nat outside - NAT inside source and access list:
ip nat inside source list pool
PAT (Overloading) Configuration
- Purpose: allows multiple devices on a private network to share a single or a small number of public IP addresses for Internet access
- Single IP NAT pool creation:
ip nat pool netmask - NAT inside source with overload:
ip nat inside source list pool overload - Interface configuration:
interface Ethernet0,ip address,ip nat inside - Interface configuration:
interface Serial0,ip address,ip nat outside - Access list for internal network:
access-list permit
Assigning IPv6 Addresses
- Manually assigning an IPv6 address to an interface uses the command
ipv6 address / - Example:
ipv6 address 2001:db8:3c4d:1:0260:d6FF:FE73:1987/64
Using EUI-64 for Interface ID
- EUI-64 (Extended Unique Identifier) uses a device's MAC address to create a unique 64-bit interface identifier
- Command:
ipv6 address / eui-64 - EUI-64 pads the MAC address to create a unique identifier
- Example: MAC address
0060:d673:1987becomes0260:d6FF:FE73:1987after padding
IPv6 Autoconfiguration
- Autoconfiguration allows devices to assign themselves a link-local unicast address and a global unicast address
- Command:
ipv6 address autoconfig - The interface listens for Router Advertisements (RAs) and assigns itself a global address using EUI-64 format
DHCPv6 (Stateful Configuration)
- Initially, devices listen for Router Advertisements (RAs) to get prefix information
- If no router is found, the client sends a DHCPv6 Solicit message with a destination address of
ff02::1:2
IPv6 Addressing Schemes
- Global unicast address
- Multicast address
- Link-local address
- Unique local address
- EUI-64 address
- Autoconfiguration
Reasons to Transition to IPv6
- Communication limits of IPv4
- Bandwidth and IP conservation
- Address exhaustion (IPv4 addresses nearly depleted)
- Growing online population
IPv6 Protocols
- OSPF (Open Shortest Path First) Version 3 supports IPv6 addressing and features
- ICMP (Internet Control Message Protocol) Version 6 expanded to handle IPv6 operations
- NDP (Neighbor Discovery Protocol) replaces ARP (Address Resolution Protocol) in IPv6
ICMPv6
- Type field specifies the ICMPv6 message type
- Code field provides further granularity about the message type
- Data field contains the ICMPv6 message payload
Router Solicitation and Advertisement
- IPv6 hosts send a Router Solicitation (RS) to all routers on the same link using the multicast address
FF02::2 - Routers respond with a unicast Router Advertisement (RA) to the requesting host
IPv6 Static and Default Routing
- Static route on Corp router guides traffic to a specific network
- Default route on Branch router handles all other destinations using a specified next-hop IPv6 address or exit interface
OSPFv3
- Link-state routing protocol that divides an internetwork or AS into areas, creating a hierarchy
- Router ID (RID) and area ID are assigned manually in OSPFv3
- Adjacencies and next-hop attributes use link-local addresses
- OSPFv3 uses multicast traffic to send updates and acknowledgments with addresses
FF02::5for OSPF routers andFF02::6for OSPF-designated routers
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Description
Learn about Network Address Translation (NAT) and its types, including Static NAT, used to conserve IP addresses and enable internet access without unique IPs.
