Great pluralsight course on networking for developers. I always forget this stuff.
Concepts
DHCP
DHCP forms the basis of the functionality that allows your machine to automatically get and ip address and subnet mask.
DHCP stands for Dynamic Host Configuration Protocol.
DHCP has different messages that it can send, these include:
- DHCPDISCOVER
- DHCPOFFER
- DHCPREQUEST
- DHCPACK
- DHCPNAK
- DHCPDECLINE
- DHCPINFORM
- DHCPRELEASE
DNS Nameservers
Domain Name System (DNS) is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network.
It is the service that when you ping www.google.com translates that address into an ip address.
Subnets
Host Files
You can overwrite dns by customizing your host file.
The host file is located at…
C:\Windows\System32\drivers\etc
Changing the host file will clear the local cache and cause it to be repopulated with the settings in the host file.
Tools
ping
ipconfig - Windows
Display all the cached records on your local machine including the time till that cached record expires.
ipconfig /displaydns
Clear local DNS cache
ipconfig /flushdns
dig - Linux
Short for Domain Information Groper, dig is a network administration tool for querying DNS name servers.
- Powerful
- Lots of functions
Simple query
dig markpearl.co.za
Querying a specific name server
dig @ns1.dnsimple.com markpearl.co.za
Tracing to make iterative queries
dig +trace markpearl.co.za
host - Linux
host is used for converting domain names to ip addresses and the other way around.
- Simple & quick
- Doesn’t have a lot of functions
host markpearl.co.za
nslookup - Linux & Windows
Allows you to get dns responses from the command line.
- One of the oldest tools for DNS lookup
- Does not use the local resolver provided by the OS, uses its own internal resolver to make DNS queries
- Sometimes produces confusing or inconsistent results
e.g. nslookup markpearl.co.za
returns 192.168.0.1
You can compare dns server responses using this tool. You can specify a specific dns server to query by doing the following:
nslookup
server xxx.xxx.xxx.xxx
Going forward any nslookup queries will be done against the dns server at ip address xxx.xxx.xxx.xxx
nslookup by default returns a-record types, this can be changed by…
nslookup
set type=NS
There are different types inclusing MX, NS, CNAME, AAAA, etc
