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
Command ipconfig /all (Show local IP configuration on current DEVICE)
Command nslookup (Shows IP information for a given DNS entry)
WIRESHARK CAPTURE of above COMMANDS
Command ipconfig /displaydns (Displays DNS cache)
Command ipconfig /flushdns (Clears DNS cache)
HOSTS Files
WINDOWS HOSTS location
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>
Command show hosts
Command ip name-server and ip domain lookup
COMMAND REVIEW:
