This 6-9 Yu

The primary use of NAT (Example: Translating dozens of private home IPs to a single public IP from your ISP)

In NAT terminology, the set of networks that is subject to translation (Example: Your private home or corporate LAN, such as 192.168.1.0/24)

In NAT terminology, all networks other than the ones subject to translation (Example: The public internet)

The perspective from which NAT terminology is always applied (Example: The perspective is from the NAT router translating your PC's IP)

The address of the device which is being translated by NAT (Example: 192.168.1.10 [Inside Local] or its translated public IP 203.0.113.5 [Inside Global])

The address of the destination device (Example: The public IP 8.8.8.8 of a Google server you are trying to reach)

Any address that appears on the inside portion of the network (Example: An internal IP address like 10.0.0.5)

Any address that appears on the outside portion of the network (Example: A public, routable IP address like 198.51.100.1)

Uses a one-to-one mapping of local and global addresses (Example: Permanently mapping an internal web server at 192.168.1.50 to a specific public IP 203.0.113.10 so the internet can always reach it)

Uses a pool of public addresses and assigns them on a first-come, first-served basis (Example: A pool of 5 public IPs shared among 50 employees; only 5 can access the internet at the exact same time)

Maps multiple private IPv4 addresses to a single public IPv4 address or a few addresses (Example: A home network of 10 devices sharing one public IP by using different source port numbers, like 203.0.113.5:1055 and 203.0.113.5:1056)

The reason NAT increases forwarding delays

The reason NAT complicates the use of tunneling protocols like IPsec

Command to display all static translations that have been configured and dynamic translations created by traffic

Command to clear dynamic entries before the timeout has expired

Developed with the intention of making NAT for IPv4 unnecessary

Similar to RFC 1918 private addresses in IPv4 but have a different purpose (Example: Addresses starting with fd00:/8, used strictly for internal communications)

Provides for protocol translation between IPv4 and IPv6

Required to connect beyond the boundary of the LAN (Example: Connecting a headquarters in New York to a branch in London)

A connection that is dedicated to a single customer (Example: A leased fiber line exclusively used by one company)

A connection typically provided by an ISP or telecommunications service provider using the internet (Example: A standard broadband internet connection from Comcast or AT&T)

Logical topologies used to implement WANs

Provides redundancy and increases network availability by negotiating separate SLAs with two different service providers (Example: A hospital using AT&T as its primary internet connection and Verizon as a backup)

Enables the company to use the internet to securely connect with employees and facilities around the world

Recognized authorities that define and manage modern WAN standards

Layer 1 optical fiber protocol standards

Layer 2 protocols that define how data will be encapsulated into a frame

Transmits bits sequentially over a single channel (Example: Sending bits one by one down a single wire)

Simultaneously transmits several bits using multiple wires (Example: Sending 8 bits at once across 8 separate wires inside a cable)

The two most common types of circuit-switched WAN technologies

Common types of packet-switched WAN technologies

Define how to transfer multiple data, voice, and video communications over optical fiber using lasers or LEDs over great distances

Provided circuit-switched connections (Example: Traditional dial-up telephone networks)

A circuit-switching technology that enables the PSTN local loop to carry digital signals

Segments data into packets that are routed over a shared network (Example: Modern internet traffic where data is broken into IP packets and shares routers dynamically with other traffic)

A simple Layer 2 NBMA WAN technology used to interconnect enterprise LANs

A technology built on a cell-based architecture capable of transferring voice, video, and data through private and public networks

Modern WAN connectivity options

A high-performance service provider WAN routing technology capable of encapsulating all types of protocols to interconnect clients (Example: A service provider tagging packets with short labels to rapidly switch traffic between a company's remote branches)

An alternative to using dedicated WAN options

Examples of wired broadband connectivity

Examples of wireless broadband

A high-speed, always-on connection technology that uses existing twisted-pair telephone lines to provide IP services

A high-speed always-on connection technology that uses a cable company coaxial cable to provide IP services

Newer developments in wireless technology

Routed through the internet from the private network of the company to the remote site or employee host (Example: An encrypted IPsec tunnel carrying confidential company data over the public internet)

ISP connectivity options

Keeps data confidential while it is transported across the public network by encrypting traffic (Example: Cisco AnyConnect)

Benefits of VPNs

Lets remote and mobile users securely connect to the enterprise by creating an encrypted tunnel using IPsec or SSL (Example: An employee working from a coffee shop securely logging into corporate servers)

Used to connect networks across an untrusted network such as the internet (Example: An encrypted tunnel directly linking a router in a branch office to a router at headquarters)

The VPN terminating device in a site-to-site VPN (Example: A Cisco ASA firewall or an edge router)

A non-secure site-to-site VPN tunneling protocol (Example: Encapsulating routing updates to send them over a WAN, without actually encrypting the data)

A Cisco software solution for easily building multiple, dynamic, scalable VPNs (Example: A hub router dynamically creating tunnels to hundreds of remote spoke branches automatically as needed)

Simplifies the configuration process required to support multiple sites and remote access

Protects and authenticates IP packets between source and destination

Layers at which IPsec can protect traffic

Provided by the IPsec framework

Protocols used by IPsec to encapsulate packets

Determines the degree of confidentiality in IPsec (Example: AES-256 provides stronger confidentiality than older DES)

Provides a way for two peers to establish a shared secret key over an insecure channel

Created by voice and live video transmissions, prompting a need for Quality of Service (QoS)

What happens without QoS mechanisms in place during congestion

The reason queuing packets causes delay

Two types of delays

Sources of delay

The variation in the delay of received packets (Example: A VoIP call sounding robotic or choppy because the voice packets are arriving at inconsistent intervals)

Traffic that is smooth and benign, but sensitive to drops and delays (Example: A VoIP phone call)

Traffic that is demanding, bursty, greedy, drop sensitive, and delay sensitive (Example: A live Zoom meeting or streaming an HD training video)

Traffic that uses TCP applications, can retransmit data, and is not sensitive to drops and delays (Example: Downloading a PDF or sending an email)

When the QoS policy implemented by the network administrator becomes active

A congestion management tool that can buffer, prioritize, and reorder packets before transmission

Buffers and forwards packets in the order of their arrival with no concept of priority (Example: A grocery store checkout line where everyone is served in the exact order they arrived)

An automated scheduling method that provides fair bandwidth allocation by applying weights to identified traffic

Extends standard WFQ functionality to provide support for user-defined traffic classes based on match criteria

Brings strict priority queuing (PQ) to CBWFQ (Example: Reserving a strict priority lane specifically for voice traffic so calls never drop during heavy congestion)

The three models for implementing QoS

Architecture model developed to meet the needs of real-time applications (Example: Using RSVP to reserve exact bandwidth across the entire network path before sending any data)

Specifies a simple and scalable mechanism for classifying and managing network traffic, overcoming previous model limitations (Example: Tagging packets with DSCP values at the edge of the network so internal routers know how to prioritize them on the fly)

The three categories of QoS tools

Determines the class of traffic to which packets or frames belong (Example: Identifying all traffic destined for TCP port 80 as 'Web Traffic')

Methods of classifying traffic flows at Layer 2 and 3

Used to classify traffic at Layers 4 to 7 (Example: Automatically recognizing YouTube traffic by its payload even if it uses random ports)

Includes queuing and scheduling methods where excess traffic is buffered or queued

Helps monitor network traffic loads to anticipate and avoid congestion at bottlenecks

A possible congestion avoidance solution included in Cisco IOS QoS (Example: Randomly dropping low-priority file download packets before a queue fills up completely, forcing TCP connections to slow down before a bottleneck happens)