4.0 CCNA - IP Services

4.3 Role of DHCP and DNS within an IP network

Configuring DHCP to an IOS router

To assign DHCP on an IOS router, you need to configure the router as a DHCP server and specify the range of IP addresses that will be assigned to devices on the network. Here is an example configuration:

Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# ip dhcp pool [pool_name]
Router(dhcp-config)# network [network_address] [subnet_mask]
Router(dhcp-config)# default-router [default_gateway_address]
Router(dhcp-config)# dns-server [dns_server_address]
Router(dhcp-config)# exit
Router(config)# interface [interface_name]
Router(config-if)# ip address [ip_address] [subnet_mask]
Router(config-if)# ip helper-address [DHCP_server_address]
Router(config-if)# end
Router#

In this example:

[pool_name] is the name of the DHCP pool.
[network_address] [subnet_mask] is the network address and subnet mask that defines the range of IP addresses that will be assigned to devices on the network.
[default_gateway_address] is the IP address of the default gateway for the network.
[dns_server_address] is the IP address of the DNS server that devices on the network will use.
[interface_name] is the name of the interface that is connected to the network where devices will receive IP addresses from the DHCP server.
[ip_address] [subnet_mask] is the IP address and subnet mask that will be assigned to the interface.
[DHCP_server_address] is the IP address of the DHCP server.

Once you have completed the configuration, you can verify that the DHCP server is functioning correctly by checking the DHCP bindings table on the router, and by checking that devices on the network are receiving IP addresses from the DHCP server.

Configuring an IOS device as DNS server

To configure an IOS device as a DNS server, you need to specify the domain names and IP addresses that will be managed by the server, and then enable the DNS service on the device. Here is an example configuration:

Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# ip domain-name [domain_name]
Router(config)# ip name-server [dns_server_address]
Router(config)# ip dns server
Router(config)# exit
Router#

In this example:

[domain_name] is the name of the domain that the DNS server will manage.
[dns_server_address] is the IP address of the DNS server.

Once you have completed the configuration, you can verify that the DNS server is functioning correctly by checking the DNS database on the router, and by using the nslookup command to resolve domain names managed by the DNS server.

DHCP provides a convenient way for network administrators to manage the assignment of IP addresses to devices on the network. When a device connects to the network, it sends a broadcast request for an IP address, which is then assigned by the DHCP server. This eliminates the need for manual configuration of IP addresses on each device and ensures that IP addresses are unique and not duplicated within the network.

DNS provides a way to translate human-readable domain names into IP addresses, allowing users to access websites and other Internet resources using memorable names. This eliminates the need for users to remember the IP addresses of every website or resource they access, and also provides a scalable way to manage the assignment of names to IP addresses for the entire Internet.

In summary, DHCP and DNS play crucial roles in managing IP addresses and domain names within a network, enabling efficient communication and ease of use for users accessing network resources.