How To Configure DNS Server On A Cisco Router

The DNS protocol is used to resolve FQDN (Fully Qualified Domain Names) to IP addresses around the world. This allows us to successfully find and connect to Internet websites and services no matter where they are. Its usefulness, however, doesn't stop there: local company and private networks also rely on DNS to operate efficiently and correctly.

In many cases, where a local DNS server is not available, we are forced to either use our ISP's DNS servers or some public DNS server, however, this can sometimes prove troublesome. Today, small low-end routers have the ability to integrate DNS functionality, making life easier, but so do Cisco routers - they simply have to be setup and you're done.

This article will show you how to configure your Cisco router to provide DNS services to your network, and make all clients use it as a DNS server. Our easy to follow step-by-step process ensures you'll understand the process and have it running within minutes.

Example Scenario

Consider the following network diagram. This is our example network, we'd like to enable the DNS Service so our workstations can properly resolve Internet domains but also local network names.

First step is to enable the DNS service on the router:

R1# configure terminal
R1(config)# ip dns server

Next, we need to configure the router with a public name-server, this will force the router to perform recursive DNS lookups, in other words, for every request it receives from our workstations the router will try to find the answer by asking as many DNS servers it needs, and finally return with an answer:

R1(config)# ip name-server 4.2.2.5
R1(config)# ip name-server 4.2.2.6

The Cisco IOS will allow you to enter up to 6 different name servers (essentially DNS servers). Usually you would use your ISP's DNS server to ensure you have quick responses, then place a few free public DNS servers such as the ones above. This will ensure that you'll get a DNS response from either your ISP or public DNS servers.

Next step is to configure your DNS server with the host names of your local network, this way when Alan's PC trys to ping or connect to Wayne, the router will successfully resolve its netbios name to the appropriate IP address:

R1(config)# ip host alan 192.168.1.10
R1(config)# ip host john 192.168.1.11
R1(config)# ip host wayne 192.168.1.12

If you now try to ping 'wayne' directly from your router's CLI prompt, you should receive an answer:

R1# ping wayne

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.12, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

At this point, you can configure your workstations to use your router's IP address as the primary DNS server:

VIRTUAL PRIVATE NETWORKS (VPN)

VIRTUAL PRIVATE NETWORKS (VPN)

What is VPN?

• Virtual Private Network is a type of private network that uses public telecommunication,such as the Internet, instead of leased lines to communicate.
• Became popular as more employees worked in remote locations.
• Terminologies to understand how VPNs work. Private Networks vs.Virtual Private Networks
• Employees can access the network (Intranet)from remote locations.
• Secured networks.
• The Internet is used as the backbone for VPNs

Brief Overview of How it Works

• Two connections – one is made to the Internet and the second is made to the VPN.
• Datagrams – contains data, destination and source information.
• Firewalls – VPNs allow authorized users to pass through the firewalls.
• Protocols – protocols create the VPN tunnels. Four Critical Functions
• Authentication – validates that the data was sent from the sender.
• Access control – limiting unauthorized users from accessing the network.
• Confidentiality – preventing the data to be read or copied as the data is being transported.
• Data Integrity – ensuring that the data has not been altered

Encryption

• Encryption -- is a method of “scrambling”data before transmitting it onto the Internet.
• Public Key Encryption Technique
• Digital signature – for authentication

Tunneling

A virtual point-to-point connection made through a public network. It transports encapsulated datagrams.
Two types of end points:
 

• Remote Access
• Site-to-Site

Four Protocols used in VPN

• PPTP -- Point-to-Point Tunneling Protocol
• L2TP -- Layer 2 Tunneling Protocol
• IPsec -- Internet Protocol Security
• SOCKS – is not used as much as the ones above

Types of Implementations

What does “implementation” mean in VPNs
3 types

• Intranet – Within an organization
• Extranet – Outside an organization
• Remote Access – Employee to Business

Device Types

 3 types

•  Hardware
•  Firewall
• Software

Applications: Remote Access

• Encrypted connections between mobile or remote users and their corporate networks
• Remote user can make a local call to an ISP, as opposed to a long distance call to the corporate remote access server.
• Ideal for a telecommuter or mobile sales people.
• VPN allows mobile workers & telecommuters to take advantage of broadband connectivity.

        Healthcare: enables the transferring of confidential patient information within the medical facilities &     health care provider

• Manufacturing: allow suppliers to view inventory & allow clients to purchase online safely
• Retail: able to securely transfer sales data or customer info between stores & the headquarters
• Banking/Financial: enables account information to be transferred safely within departments & branches
• General Business: communication between remote employees can be securely exchanged