CCNA Configuring PPP, CHAP, AAA, DNS and HTTP Website - CCNA

CCNA Configuring PPP, CHAP, AAA, DNS and HTTP Website


Domain Name Server (DNS)

Each computer on the Internet is assigned a unique address, called an IP address. A typical IP address looks like this: 199.123.456.7

It is very difficult to keep in mind the IP addresses of all the websites we visit daily. Words are easier to remember than strings of numbers. This is where domain names come into the picture. When you visit a website, all you need to know is its URL. Computers remember numbers, and DNS helps us convert the URL into an IP address that the computer can understand.

When you type in domain.com into your browser, the browser first needs to get the IP address of www.domain.com. The browser contacts a DNS server to query the location of the server where the webpages are stored. Think of it as a directory service of IP address.

The classic phonebook directory analogy, you need to find the company “Joe’s Bookstore”, you look in the directory and see that it is located on 123 Main Street. Then you go to the address to visit the store.

DNS, which stands for domain name system, controls your domain name’s website and email settings. When visitors go to your domain name, its DNS settings control which company’s server it reaches out to.

For example, if you use GoDaddy’s DNS settings, visitors will reach GoDaddy’s servers when using your domain name. If you change those settings to user another company’s servers, visitors will reach them instead of us when visiting your domain.

CHAP

CHAP (Challenge-Handshake Authentication Protocol) is a more secure procedure for connecting to a system than the Password Authentication Procedure (PAP). Here’s how CHAP works:

  1. After the link is made, the server sends a challenge message to the connection requestor. The requestor responds with a value obtained by using a one-way hash function.
  2. The server checks the response by comparing it its own calculation of the expected hash value.
  3. If the values match, the authentication is acknowledged; otherwise theconnection is usually terminated.

At any time, the server can request the connected party to send a new challenge message. Because CHAP identifiers are changed frequently and because authentication can be requested by the server at any time, CHAP provides more security than PAP. RFC1334 defines both CHAP and PAP.

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