CCNA Notes

200-301 Exam Prep

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1Networking Devices2Interfaces And Cables3OSI Model and TCP/IP Suite4Intro to the CLI5Ethernet LAN Switching - Part 16Ethernet LAN Switching - Part 27IPv4 Addressing - Part 18IPv4 Addressing - Part 29Switch Interfaces10The IPv4 Header11Routing Fundamentals - Part 111Static Routing - Part 212Life of a Packet13Subnetting - Part 114Subnetting - Part 215Subnetting (VLSM) - Part 316VLANs - Part 117VLANs - Part 218VLANs - Part 319DTP / VTP20Spanning Tree Protocol - Part 121Spanning Tree Protocol - Part 222Rapid Spanning Tree Protocol23Etherchannel24Dynamic Routing25RIP / EIGRP26OSPF - Part 127OSPF - Part 228OSPF - Part 329First Hop Redundancy Protocol30TCP and UDP31IPv6 - Part 132IPv6 - Part 233IPv6 - Part 334Standard Access Control List35Extended Access Control List36CDP and LLDP37NTP - Network Time Protocol38DNS - Domain Name System39DHCP - Dynamic Host Configuration Protocol40SNMP - Simple Network Management Protocol41SYSLOG42SSH - Secure Shell43FTP and TFTP44NAT (Static) - Part 145NAT (Dynamic) - Part 246QoS (Voice VLAN) - Part 147QoS (Quality of Service) - Part 248Security Fundamentals49Port Security50DHCP Snooping51Dynamic ARP Inspection52LAN Architectures53WAN Architectures54Virtualization and Cloud - Part 154Virtualization (Containers) - Part 254Virtualization (VRF) - Part 355Wireless Fundamentals56Wireless Architectures57Wireless Security58Wireless Configuration59Introduction to Network Automation60JSON, XML, and YAML61REST APIs62Software Defined Networking63Ansible, Puppet, and Chef67CCNA Complete Cheatsheet
/FTP and TFTP
Topic 434 min read

FTP and TFTP

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43. FTP and TFTP

THE PURPOSE OF FTP / TFTP

  • FTP (File Transfer Protocol) and TFTP (Trivial File Transfer Protocol) are INDUSTRY STANDARD PROTOCOLS used to TRANSFER FILES over a NETWORK
  • They BOTH use a CLIENT-SERVER model
    • CLIENTS can use FTP / TFTP to COPY files FROM a SERVER
    • CLIENTS can use FTP / TFTP to COPY files TO a SERVER
  • As a NETWORK ENGINEER, the most common use for FTP / TFTP is in the process of UPGRADING the OPERATING SYSTEM of a NETWORK DEVICE
  • You can use FTP / TFTP to DOWNLOAD the newer version of IOS from a SERVER and then REBOOT the DEVICE with the new IOS image

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TFTP and FTP FUNCTIONS AND DIFFERENCES

TFTP

  • TFTP first standardized in 1981
  • Named “Trivial” because it’s SIMPLE and has only basic features compared to FTP
    • Only allows a CLIENT to COPY FILES to / from a SERVER
  • Was released after FTP, but not a REPLACEMENT for FTP.
    • It’s another tool to use when LIGHTWEIGHT SIMPLICITY is more important than FUNCTIONALITY
  • NO AUTHENTICATION (Username / Password) so SERVERS will respond to ALL FTP REQUESTS
  • NO ENCRYPTION. All DATA is sent PLAIN TEXT
  • Best used in a CONTROLLED environment to transfer SMALL FILES quickly
  • TFTP SERVERS listen on UDP PORT 69
  • UDP is CONNECTIONLESS and doesn’t provided RELIABILITY with RETRANSMISSIONS
  • However, TFTP has SIMILAR built-in FEATURES within the PROTOCOL itself

TFTP RELIABILITY

  • Every TFTP DATA message is ACKNOWLEDGED
    • If the CLIENT is transferring a FILE TO the SERVER, the SERVER will send ACK messages
    • If the SERVER is transferring a FILE TO the CLIENT, the CLIENT will send ACK messages
  • TIMERS are used, and if an EXPECTED message isn’t received in time, the waiting DEVICE will RESEND its previous message.

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TFTP “CONNECTIONS”

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TFTP TID (Not in the CCNA exam)

  • When the CLIENT sends the FIRST message to the SERVER, the DESTINATION PORT is UDP 69 and the SOURCE PORT is a random EPHEMERAL PORT
  • This “random port” is called a “TRANSFER IDENTIFIER” (TID) and identifies the DATA TRANSFER
  • The SERVER then also selects a RANDOM TID to use as a SOURCE PORT when it replies, NOT UDP 69
  • When the CLIENT sends the NEXT message, the DESTINATION PORT will be the SERVER’S TID, NOT UDP 69

UDP PORT 69 (TFTP) is only used at the initial request message

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FTP

  • FTP was first standardized in 1971
  • FTP uses TCP PORTS 20 and 21
  • USERNAMES and PASSWORDS are used for AUTHENTICATION, however there is NO ENCRYPTION
  • For GREATER security, FTPS (FTP over SSL / TLS) can be used (Upgrade to FTP)
  • SSH File Transfer Protocol (SFTP) can also be used for GREATER security (New Protocol)
  • FTP is MORE complex than TFTP and ALLOWS not only FILE TRANSFERS but CLIENTS can also:
    • Navigate FILE DIRECTORIES
    • ADD / REMOVE FILES
    • LIST FILES
    • etc…
  • The CLIENT sends FTP commands to the SERVER to perform these functions

FTP CONTROL CONNECTIONS

  • FTP uses TWO TYPES of connections:
    • An FTP CONTROL connection (TCP 21) is established and used to send FTP commands and replies
    • When FILES or DATA are to be transferred, separate FTP DATA (TCP 20) connections are established and terminated as needed

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ACTIVE MODE FTP DATA CONNECTIONS

  • The DEFAULT method of establishing FTP DATA connections is ACTIVE MODE in which the SERVER initiates the TCP connection.

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  • In FTP PASSIVE MODE, the CLIENT initiates the DATA connection.
    • This is often necessary when the CLIENT is behind a FIREWALL, which could BLOCK the INCOMING CONNECTION from the SERVER

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FTP VERSUS TFTP

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IOS FILE SYSTEMS

  • A FILE SYSTEM is a way of controlling how DATA is STORED and RETRIEVED
  • You can VIEW the FILE SYSTEM of a Cisco IOS DEVICE with show file systems

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USING FTP / TFTP IN IOS

  • You can VIEW the current version of IOS with show version

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  • You can VIEW the contents of flash with show flash

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COPYING FILES WITH TFTP

STEP 1

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STEP 2

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STEP 3

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COPYING FILES WITH FTP

STEP 1

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STEP 2 and 3 identical to TFTP above

COMMAND SUMMARY

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