CONFIGURE CISCO ROUTER AS DNS SERVER

Domain Name Servers (DNS) are the Internet’s equivalent of a phone book. They maintain a directory of FQDN (Fully Qualified Domain Names) and translate them to Internet Protocol (IP) addresses. This is necessary because domain names are easy for people to remember and hence end systems access websites based on IP addresses.

In scenarios where local DNS server cannot be used, corporate customers need to be fully dependent on 3rd parties like ISP or some public DNS Server. This arrangement will have a lot of overhead and dependencies. Cisco routers have the ability to integrate DNS functionality and provide the local DNS service which gives more control to customer. Let’s understand below how the DNS service on local Cisco Router can be performed in simple steps –

Below is the reference diagram where Cisco Router R1 (192.168.0.1) will be configured with DNS Service. Also, we have 2 workstations arush and john with IPs 192.168.0.3 and 192.168.0.4 respectively. The fileserver is given the IP 192.168.0.5.

configure-cisco-router-as-dns-server

 

Step 1 –

Enable DNS service and domain lookup on the router –

R1# configure terminal
R1(config)# ip dns server
R1(config)# ip domain-lookup
Step 2 –

Configure the router with a public name-server . The DNS request from inside users will be sent to Router which will further send query to DNS servers over Internet. The IP address of the Destination is served back to the requesting workstation.

R1(config)# ip name-server 4.2.2.2
Step 3 –

Configure DNS server with the host names of your local network.In this case,when any other PC wants to ping “arush”(workstation) , the router will resolve its netbios name to the appropriate IP address. Same in case of “filerserver”.

R1(config)# ip host fileserver 192.168.0.5
R1(config)# ip host arush 192.168.0.3
Step 4 –
R1# ping arush
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/6 ms
R1# ping fileserver
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/6 ms
Step 5 –
We configure the workstations and file servers to use router’s IP address as the DNS server as below –

configure-cisco-router-as-dns-server

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