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Telnet & SSH

Telnet

Telnet is a network protocol that allows a user to communicate with a remote device. It is a virtual terminal protocol used mostly by network administrators to remotely access and manage devices. Administrator can access the device by “telnetting” to the IP address or hostname of a remote device.
 
To use telnet, you must have a software (Telnet client) installed. On a remote device, a Telnet server must be installed and running. Telnet uses TCP port 23.
 
One of the greatest disadvantages of this protocol is that all data, including usernames and passwords, is sent in clear text, which is a potential security risk. This is the main reason why Telnet is rarely used today and is being replaced by a much secure protocol called SSH.
 
The word “telnet” can also refer to the software that implements the telnet protocol.
On Windows, you can start a Telnet session by typing the telnet IP_ADDRESS or HOSTNAME command:
 
telnet windows

 

 

SSH (Secure Shell)

SSH is a network protocol used to remotely access and manage a device. The key difference between Telnet and SSH is that SSH uses encryption, which means that all data transmitted over a network is secure from eavesdropping.
 
Like Telnet, a user accessing a remote device must have an SSH client installed. On a remote device, an SSH server must be installed and running. SSH uses TCP port 22 by default.
 
SSH relies on public key cryptography for its encryption.
 
Here is an example of creating an SSH session using Putty, a free SSH client:
 
putty
 
NOTE – SSH is the most common way to remotely access a Cisco device.
Jan 26, 2016upravnik
DHCP & DNSFTP & TFTP
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CONTENT #1
  • Networking basics
    • What is a network?
    • OSI & TCP/IP models
    • Encapsulation
    • Ethernet
    • Ethernet frame
    • MAC & IP addresses
    • Unicast, multicast, and broadcast addresses
    • Network devices
    • Half duplex and full duplex
    • IEEE Ethernet standards
    • Cisco three-layer hierarchical model
  • Cabling
    • Types of Ethernet cabling
    • Types of Ethernet cables
  • Types of networks
    • Wide area network
    • Local area network & Metropolitan area network
  • IP addressing
    • Types of IP addresses
    • Classes of IP addresses
    • Subnetting explained
    • Subnet mask
    • Create subnets
  • Network tools
    • Ping
    • Traceroute
  • Network protocols
    • TCP/IP suite of protocols
    • TCP explained
    • UDP explained
    • Ports explained
    • ARP
    • DHCP & DNS
    • Telnet & SSH
    • FTP & TFTP
    • SNMP (Simple Network Management Protocol)
    • HTTP & HTTPS
    • NTP (Network Time Protocol)
    • APIPA (Automatic Private IP Addressing)
    • ICMP (Internet Control Message Protocol)
    • IP header
  • Cisco IOS
    • Cisco IOS overview
    • Power on a Cisco device
    • IOS command modes
    • Get help in IOS
    • Running & startup configuration
    • IOS basic commands
    • Configure descriptions
    • Run privileged commands within global config mode
    • Ports on an IOS device
    • Pipe character in IOS
    • IOS boot sequence
    • Backing up IOS configuration
  • IP routing
    • What is IP routing?
    • Connected, static & dynamic routes
    • Administrative distance & metric
    • Routing protocols
  • RIP
    • RIP overview
    • Configuring RIPv2
    • RIP loop prevention
  • EIGRP
    • EIGRP overview
    • EIGRP configuration
    • EIGRP automatic & manual summarization
    • EIGRP authentication & load balancing
    • EIGRP summary
  • OSPF
    • OSPF overview
    • OSPF configuration
    • Designated & Backup Designated Router
    • OSPF authentication
    • OSPF summarization
    • OSPF summary
    • Differences between OSPF and EIGRP
  • LAN switching
    • Layer 2 switching
    • Collision & broadcast domain
    • CSMA/CD
  • VLAN
    • What is a VLAN?
    • Configuring VLANs
    • Configuring access & trunk ports
    • Frame tagging
    • IEEE 802.1Q
    • Inter-Switch Link (ISL)
CONTENT #2
  • ACLs
    • What are ACLs?
    • Types of ACLs
    • Configuring standard ACLs
    • Configuring extended ACLs
  • NAT
    • What is NAT?
    • Static NAT
    • Dynamic NAT
  • IPv6
    • What is IPv6?
    • IPv6 address format
    • Types of IPv6 addresses
    • IPv6 unicast addresses
    • IPv6 global unicast addresses
    • IPv6 unique local addresses
    • IPv6 link-local addresses
    • IPv6 multicast addresses
    • IPv6 address prefixes
    • IPv6 interface identifier
    • IPv6 transition options
    • IPv6 routing protocols
    • How to configure IPv6
    • RIPng
    • Differences between IPv4 and IPv6
  • Miscellaneous
    • Wildcard masks
    • Setting up Telnet
    • Setting up SSH
    • Port security
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