Basic Networking Protocols: Part 2

Welcome to Part 2 of Basic Networking Protocols! I’m here to fill you in on some essential knowledge that every Cisco Network Professional should have a solid understanding of.

In today’s article, I will talk about two application layer protocols which are extensively used in every kind of network infrastructure: Domain Name Service (DNS) and Dynamic Host Configuration Protocol (DHCP).

In Part 1 of Basic Networking Protocols I covered the most important protocol suite, that you should have a good understanding of by now: Transmission Control Protocol (TCP) / Internet Protocol (IP).

If you missed this article, go ahead and take a look at it first before moving on to the information in the second part — it will give you some good background information and will help you get the whole picture.

 

Domain Name Service (DNS)

DNS protocol is used extensively nowadays due to the existence of the Internet. It is responsible for resolving hostnames to IP addresses. Requesting to view web pages on the Internet wouldn’t be so easy if instead of text URLs like this one: www.trainsignaltraining.com we had to use IP addresses like this: 69.16.232.158.

Believe me, if you had to remember this type of numerical addressing for visiting every single web page you wouldn’t be visiting them at all. DNS has been invented to save the day — or should I say, the century!

Web servers are identified the same way as every other networking device — they possess an IP address. In order for users to direct their requests to the appropriate web server, the DNS protocol is responsible for translating Domain Names to their respective IP addressing schemes, so that user requests can be directed to the intended IP address of the web server.

Note: One important thing to remember when troubleshooting potential DNS problems is that if you can ping a host using its IP address then you should also ping that device using its domain name. If not, then you have a DNS problem.

Cisco CCENT 1

 
Cisco CCENT 2

 

Dynamic Host Configuration Protocol (DHCP)

In a large network infrastructure and even in the small ones with 10-20 hosts, having to manually configure IP addresses on each individual host would be impractical. DHCP comes to the rescue in this case.

DHCP is responsible for providing an IP address along with a great deal of extra information when a client host requests an IP address from the DHCP server. Among the information that a DHCP server can provide to client hosts is the following:

  • IP address
  • Subnet mask
  • DNS server address
  • Default gateway
  • Static routes

A DHCP reply message sent from a DHCP server to a DHCP client is shown below. Observe the batch of information provided.

Cisco CCENT 3

 

Final Thoughts on Networking Protocols

I hope that through these two articles you were able to expand your knowledge of the capabilities and operation of TCP and IP protocols. You will definitely need this information as you steadily dig deeper into networking paths.

Moreover, you should have recognized by now the beneficial contribution of both DHCP and DNS protocols to the smooth and simplified operation of internetworks. All of us, as users, have greatly benefited from the operation of these protocols. In a way, we can be grateful for them.

 

 

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