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
/DNS - Domain Name System
Topic 382 min read

DNS - Domain Name System

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38. DNS (Domain Name System)

THE PURPOSE OF DNS

  • DNS is used to resolve human-readable names (google.com) to IP ADDRESSES
  • Machines such as PCs don’t use names, they use ADDRESSES (ie: IPv4/IPv6)
  • Names are much easier for us to use and remember than IP ADDRESSES
    • What is the IP ADDRESS of youtube.com ?
  • When you type ‘youtube.com` into a web browser, your device will ask a DNS SERVER for the IP ADDRESS of youtube.com
  • The DNS SERVER(S) your DEVICE uses can be manually configured or learned via DHCP

BASIC FUNCTIONS OF DNS

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Command ipconfig /all (Show local IP configuration on current DEVICE)

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Command nslookup (Shows IP information for a given DNS entry)

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WIRESHARK CAPTURE of above COMMANDS

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Command ipconfig /displaydns (Displays DNS cache)

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Command ipconfig /flushdns (Clears DNS cache)

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HOSTS Files

WINDOWS HOSTS location

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CONFIGURING DNS IN CISCO IOS

  • For HOSTS in a NETWORK to use DNS, you don’t need to configure DNS on the ROUTERS.
    • They will simply FORWARD the DNS messages like any other packets
  • However, a CISCO ROUTER can be configured as a DNS SERVER, although it’s rare
    • If an INTERNAL DNS SERVER is used, usually it’s a WINDOWS or LINUX SERVER
  • A CISCO ROUTER can also be configured as a DNS CLIENT

Command ip dns server and ip host <hostname> <ip address>

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Command show hosts

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Command ip name-server and ip domain lookup

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COMMAND REVIEW:

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