Setting Up DHCP and DNS Servers for Local Networking

1. DHCP Server Setup

A DHCP (Dynamic Host Configuration Protocol) server automatically assigns IP addresses to devices (clients) on a network, eliminating the need to manually configure each device.

Steps to Set Up a DHCP Server on a Linux Server:

Install the DHCP server: On a Linux server, you can install the ISC DHCP Server using the following commands:
```
sudo apt update
sudo apt install isc-dhcp-server
 
 2.	Configure the DHCP server:
```

The DHCP configuration file is typically located at /etc/dhcp/dhcpd.conf. Edit it to define the network range and settings. Example of the configuration:

sudo nano /etc/dhcp/dhcpd.conf

Add the following configuration:

Define the subnet and range of IP addresses to be assigned to clients

subnet 192.168.1.0 netmask 255.255.255.0 { range 192.168.1.100 192.168.1.200; # IP range for clients option routers 192.168.1.1; # Gateway IP option domain-name-servers 192.168.1.1; # DNS server address option domain-name "localnetwork"; # Network domain name default-lease-time 600; # Lease time in seconds max-lease-time 7200; # Max lease time in seconds }

3.	Define the network interface:

The server needs to know which network interface it should listen on. Open /etc/default/isc-dhcp-server to specify the interface (e.g., eth0):

sudo nano /etc/default/isc-dhcp-server

Change the line to:

INTERFACESv4="eth0"

4.	Restart the DHCP service:

After configuring, restart the DHCP server to apply the changes:

sudo systemctl restart isc-dhcp-server

5.	Check the status:

To verify if the DHCP server is running:

sudo systemctl status isc-dhcp-server

DNS Server Setup

A DNS server is responsible for resolving domain names to IP addresses. Here, we’ll set up a simple DNS server using BIND (Berkeley Internet Name Domain) on a Linux system.

Steps to Set Up a DNS Server Using BIND: 1. Install BIND (DNS Server): Install the BIND9 package using the following commands:

sudo apt update sudo apt install bind9 bind9utils bind9-doc

2.	Configure BIND for Local DNS:

The main configuration file for BIND is /etc/bind/named.conf.local. You need to define your local DNS zones here. Example configuration for a local domain:

sudo nano /etc/bind/named.conf.local

Add the following lines for your local domain (localnetwork):

zone "localnetwork" { type master; file "/etc/bind/db.localnetwork"; # Path to your local DNS file };

3.	Create the Zone File:

Now, create a zone file that defines how domain names in the localnetwork domain will be resolved.

sudo nano /etc/bind/db.localnetwork

Example contents for the db.localnetwork file:

$TTL 604800 @ IN SOA ns1.localnetwork. admin.localnetwork. ( 2025021701 ; Serial 604800 ; Refresh 86400 ; Retry 2419200 ; Expire 604800 ) ; Negative Cache TTL

; Name servers @ IN NS ns1.localnetwork.

; A records for your local devices ns1 IN A 192.168.1.1 server IN A 192.168.1.2

This defines a DNS zone for localnetwork, with an ns1 and a server host.

4.	Configure DNS Resolver:

You need to make sure that BIND uses the correct resolver. Edit /etc/bind/named.conf.options:

sudo nano /etc/bind/named.conf.options

Example to use a public DNS resolver (like Google’s DNS):

options { directory "/var/cache/bind"; forwarders { 8.8.8.8; # Google's DNS 8.8.4.4; # Google's secondary DNS }; allow-query { any; }; };

5.	Restart BIND Service:

After the configuration is complete, restart the DNS service:

sudo systemctl restart bind9

6.	Verify DNS Configuration:

To check if your DNS server is working, you can use the dig command to query the local domain:

dig @192.168.1.1 server.localnetwork

It should return the IP address 192.168.1.2 for the server host.

Summary

DHCP Setup: • DHCP Server automatically assigns IP addresses to devices on the network. • Configuration involves editing /etc/dhcp/dhcpd.conf to define IP ranges, gateways, and DNS servers.

DNS Setup: • DNS Server translates domain names into IP addresses. • Configuration involves setting up BIND, creating zone files, and defining local domain settings.

Both DHCP and DNS servers simplify network management and ensure efficient IP address allocation and domain resolution.

Networking Concepts Azure Linux