# Cisco IOS Configure Router as DNS Server #### Network Topology [![image.png](https://bookstack.taylorhome.run/uploads/images/gallery/2022-12/scaled-1680-/Ldtimage.png)](https://bookstack.taylorhome.run/uploads/images/gallery/2022-12/Ldtimage.png) To create this topology, I used GNS3 instead of Cisco Packet Tracer because Packet Tracer routers do not simulate the "ip dns server" command. In the above network Router0 is being configured as a DNS server. Through the configuration of Router0 I wanted to not only demonstrate the ability for the router to resolve local hosts on the network, but I also wanted to show how DNS resolution that Router0 was unable to do could be forwarded to a real DNS server (1.1.1.1) on the Internet. In this way Router0 has been configured to forward unknown requests to the Cloudflare and APNIC's DNS server at 1.1.1.1. I also decided to use a real Windows 2016 Server appliance in the topology. I could have just as easily used another VPCS QEMU device, but it gave me an opportunity to revisit GNS3 Windows appliances. Also, it is not the best practice to use a networking router as the DNS server, but it can be done as this shows. #### Router0 Configuration Commands Router0>enable Router0#configure terminal Router0(config)# interface gigabitEthernet 0/0 Router0(config-if)#ip address 192.168.10.1 255.255.255.0 Router0(config-if)#no shutdown Router0(config-if)#interface gigabitEthernet 0/1 Router0(config-if)#ip address 172.16.1.1 255.255.255.248 Router0(config-if)#no shutdown Router0(config-if)#exit Router0(config)#ip dns server Router0(config)#ip domain-name local Router0(config)#ip name-server 1.1.1.1 Router0(config)# ip host fileserver.local 192.168.10.2 Router0(config)# ip host pc1.local 192.168.10.3 Router0(config)# ip host pc2.local 192.168.10.4 Router0(config)# ip host router0.local 192.168.10.1 Router0(config)# ip host router1.local 172.16.1.2 Router0(config)# ip host router2.local 172.16.2.1 Router0(config)# ip default-network 192.168.2.0 Router0(config)# router ospf 1 Router0(config-router)# network 172.16.1.0 0.0.0.7 area 0 Router0(config-router)# network 192.168.10.0 0.0.0.255 area 0 #### Router1 Configuration Commands Router1>enable Router1#configure terminal Router1(config)# interface gigabitEthernet 0/0 Router1(config-if)#ip address 172.16.1.2 255.255.255.248 Router1(config-if)#no shutdown Router1(config-if)#interface gigabitEthernet 0/1 Router1(config-if)#ip address 172.16.2.2 255.255.255.248 Router1(config-if)#no shutdown Router1(config-if)#exit Router1(config)#ip name-server 172.16.1.1 Router1(config)# ip default-network 192.168.2.0 Router1(config)# router ospf 1 Router1(config-router)# network 172.16.1.0 0.0.0.7 area 0 Router1(config-router)# network 172.16.2.0 0.0.0.7 area 0 #### Router2 Configuration Commands Router2>enable Router2#configure terminal Router2(config)# interface gigabitEthernet 0/0 Router2(config-if)#ip address dhcp Router2(config-if)#no shutdown Router2(config-if)#ip nat outside Router2(config-if)#interface gigabitEthernet 0/1 Router2(config-if)#ip address 172.16.2.1 255.255.255.248 Router2(config-if)#no shutdown Router2(config-if)#ip nat inside Router2(config-if)#exit Router2(config)#ip nat inside source list 1 interface gigabitEthernet0/0 overload Router2(config)#access-list 1 permit any Router2(config)# router ospf 1 Router2(config-router)# network 192.168.2.0 0.0.0.255 area 0 Router2(config-router)# network 172.16.2.0 0.0.0.7 area 0 The configuration of nat on Router2 is so that the network can communicate to the connected network and then to the Internet through the GNS3 cloud object. I did this to demonstrate the DNS forwarder on Router0 to 1.1.1.1 Also, the IP address on gigabitEthernet 0/0 is set for DHCP as it is getting an address from my network DHCP server. You could also make this a static address if desired. If you do set a static IP address, remember to configure a gateway of last resort. The DHCP setting configures that for the interface automatically. #### Check DNS (a few ping examples) PC1>ping fileserver.local [![image.png](https://bookstack.taylorhome.run/uploads/images/gallery/2023-01/scaled-1680-/image.png)](https://bookstack.taylorhome.run/uploads/images/gallery/2023-01/image.png) PC1>ping router2.local [![image.png](https://bookstack.taylorhome.run/uploads/images/gallery/2023-01/scaled-1680-/B9zimage.png)](https://bookstack.taylorhome.run/uploads/images/gallery/2023-01/B9zimage.png) PC1>ping www.google.com [![image.png](https://bookstack.taylorhome.run/uploads/images/gallery/2023-01/scaled-1680-/NDUimage.png)](https://bookstack.taylorhome.run/uploads/images/gallery/2023-01/NDUimage.png) Check the configured DNS Hosts on Router0 Router0#show hosts [![image.png](https://bookstack.taylorhome.run/uploads/images/gallery/2023-01/scaled-1680-/30qimage.png)](https://bookstack.taylorhome.run/uploads/images/gallery/2023-01/30qimage.png) #### GNS3 File [net11 cisco router dns server.gns3](https://bookstack.taylorhome.run/attachments/6)