FTP & TFTP in Cisco Networks

Jul 8, 2025

View transcript

Overview

This lecture covers the functions, differences, and usage of FTP (File Transfer Protocol) and TFTP (Trivial File Transfer Protocol) in Cisco networks, including relevant Cisco IOS file system basics and file transfer demonstrations.

Introduction to FTP & TFTP

  • FTP and TFTP are protocols used to transfer files over a network using a client-server model.
  • Their primary use in networking is upgrading device operating systems like Cisco IOS.

TFTP: Trivial File Transfer Protocol

  • Standardized in 1981, TFTP is a simple protocol for transferring files only.
  • No authentication or encryption; uses UDP port 69 for the initial request.
  • Suitable for quick small file transfers in secure environments.
  • Implements basic reliability using acknowledgments and retransmissions (lock-step communication).
  • Uses random Transfer Identifiers (TIDs) after the initial request to manage sessions.

FTP: File Transfer Protocol

  • Standardized in 1971, FTP is more complex, supporting additional commands (listing, deleting, navigating directories).
  • Uses TCP ports 21 (control) and 20 (data).
  • Supports authentication with a username and password but has no built-in encryption.
  • FTPS (FTP Secure) adds encryption via SSL/TLS; SFTP is a different protocol entirely.
  • Two data connection modes: active (server initiates, uses port 20) and passive (client initiates, helpful behind firewalls).

FTP vs. TFTP: Key Differences

  • FTP uses TCP (reliable, connection-based); TFTP uses UDP (connectionless at Layer 4, but tracks sessions at protocol level).
  • FTP allows directory navigation and modification; TFTP can only copy files.
  • FTP requires authentication; TFTP has none.
  • FTP is suitable for more complex and secure file management; TFTP is lightweight and simple.

Cisco IOS File Systems Overview

  • Cisco devices use multiple file system types: disk (flash storage), nvram (startup-config), network (remote servers like FTP/TFTP), and opaque (internal/logical).
  • Use SHOW FILE SYSTEMS and SHOW FLASH to view file systems and contents.

File Transfer Procedures in Cisco IOS

  • Use COPY TFTP: FLASH: (or COPY FTP: FLASH:) to transfer files to device flash memory.
  • For TFTP: know server IP and filename in advance; no directory listing is possible.
  • For FTP: configure username/password on both router and server.
  • Use BOOT SYSTEM <filepath> in global config mode to set the IOS image for boot.
  • Save configuration and use RELOAD to reboot with a new IOS image.
  • Use DELETE <filepath> to remove old files from flash.

Quiz & Practice Questions Recap

  • FTP control uses TCP port 21; data uses TCP port 20.
  • TFTP file transfer command: COPY TFTP: FLASH:
  • Use FTP passive mode when the client is behind a firewall.
  • Startup-config is stored in NVRAM on Cisco devices.
  • TFTP cannot list directory contents or create directories.
  • TFTP and SNMP use UDP for connectionless transfers.

Key Terms & Definitions

  • FTP — Protocol for transferring files with authentication and advanced features over TCP ports 20 (data) and 21 (control).
  • TFTP — Simplified file transfer protocol using UDP port 69, no authentication, minimal commands.
  • FTPS — FTP over SSL/TLS, providing encrypted file transfers.
  • SFTP — Secure File Transfer Protocol using SSH, unrelated to FTP.
  • NVRAM — Non-volatile RAM storing the startup configuration on Cisco IOS devices.
  • Flash — Persistent storage for IOS images and files in Cisco devices.
  • Active/Passive Mode (FTP) — Determines which side initiates the data connection (server/client).
  • Transfer Identifier (TID) — Random UDP port assigned for each TFTP session.

Action Items / Next Steps

  • Review lecture flashcards in Anki and complete the packet tracer practice lab.
  • Practice using COPY, BOOT SYSTEM, and DELETE commands on Cisco IOS devices.
  • Understand when to use FTP vs. TFTP and their respective modes for exam preparation.

Full transcript