Pengenalan Konsep DNS Jenis DNS Server Implementasi DNS Konsep DHCP Implementasi DHCP Windows DNS/DHCP Integrasi DNS-DHCP Keamanan Troubleshooting Best Practices Studi Kasus DNS Simulator

Pertemuan 6: Konfigurasi DNS dan DHCP

1. Pendahuluan

DNS (Domain Name System) dan DHCP (Dynamic Host Configuration Protocol) adalah dua layanan jaringan fundamental yang menjadi tulang punggung infrastruktur IT modern.

Essential Skills: Memahami cara mengkonfigurasi dan mengelola kedua layanan ini adalah keterampilan essential bagi administrator sistem.
DNS

Domain Name System

"Phonebook of the Internet"
Port 53 UDP/TCP
DHCP

Dynamic Host Configuration

Automatic IP Assignment
Port 67/68 UDP

2. Domain Name System (DNS)

Apa itu DNS?
  • Sistem terdistribusi yang menerjemahkan nama domain ke alamat IP
  • "Phonebook of the Internet" - Mencari IP berdasarkan nama
  • Menggunakan port 53 (UDP untuk query, TCP untuk zone transfer)
  • Hierarchical distributed database system
DNS Resolution

google.com → 172.217.194.113

Komponen DNS:
DNS Resolver

Client yang melakukan query

Contoh: ISP resolver, Google DNS
Root Server

Server tingkat teratas

13 root servers worldwide
TLD Server

Top-Level Domain

.com, .org, .id, dll
Authoritative Server

Pemegang data domain

NS records domain
Jenis Record DNS:
Record Type Purpose Contoh TTL
A IPv4 address google.com → 172.217.194.113 300
AAAA IPv6 address google.com → 2a00:1450:4001:815::200e 300
CNAME Canonical name (alias) www → google.com 300
MX Mail exchange @ → mail.google.com 3600
NS Name server @ → ns1.google.com 172800
TXT Text information SPF, DKIM records 3600
PTR Pointer (reverse DNS) 113.194.217.172 → google.com 3600
DNS Hierarchy & Resolution Process:
Client
→
Resolver
→
Root Server
→
TLD Server
→
Authoritative
→
IP Address

3. Types of DNS Servers

Recursive Resolver

Menerima query dari client dan melakukan full resolution

Contoh:
  • Google DNS (8.8.8.8)
  • Cloudflare DNS (1.1.1.1)
  • ISP DNS servers
Fungsi:
  • Cache DNS records
  • Reduce external queries
  • Improve response time
Authoritative Nameserver

Menyimpan record untuk domain tertentu

Contoh:
  • ns1.google.com
  • ns2.cloudflare.com
  • Custom DNS servers
Fungsi:
  • Store zone files
  • Answer queries for domains
  • Domain authority
Forwarder

Meneruskan query ke server lain

Use Case:
  • Internal DNS forward to external
  • Split horizon DNS
  • Content filtering
Contoh Konfigurasi:
# BIND9 forwarders
forwarders {
  8.8.8.8;
  8.8.4.4;
};
Caching Server

Menyimpan hasil query untuk mempercepat resolusi

Benefits:
  • Reduce latency
  • Lower bandwidth usage
  • Improve reliability
Cache Management:
# View DNS cache
rndc dumpdb -cache

# Clear DNS cache
rndc flush
systemd-resolve --flush-caches

4. Implementasi DNS di Linux

BIND9 Installation:
Ubuntu/Debian
# Update dan install BIND9
sudo apt update
sudo apt install bind9 bind9utils bind9-doc

# Start service
sudo systemctl enable bind9
sudo systemctl start bind9
CentOS/RHEL
# Install BIND
sudo yum install bind bind-utils

# atau dengan dnf
sudo dnf install bind bind-utils

# Start service
sudo systemctl enable named
sudo systemctl start named
File Konfigurasi Penting:
named.conf

Main configuration file

/etc/bind/named.conf
include "/etc/bind/named.conf.options";
include "/etc/bind/named.conf.local";
named.conf.local

Local zones configuration

/etc/bind/named.conf.local
zone "company.local" {
  type master;
  file "/var/cache/bind/db.company.local";
};
named.conf.options

Global options

/etc/bind/named.conf.options
options {
  directory "/var/cache/bind";
  forwarders { 8.8.8.8; };
};
Zone File Example:
/var/cache/bind/db.company.local
; Zone file for company.local
$TTL 604800
@ IN SOA company.local. admin.company.local. (
    2024101501 ; Serial
    604800     ; Refresh
    86400      ; Retry
    2419200    ; Expire
    604800 )    ; Negative Cache TTL

; Name servers
@    IN    NS    ns1.company.local.
@    IN    NS    ns2.company.local.

; A records
ns1    IN    A    192.168.1.10
ns2    IN    A    192.168.1.11
www    IN    A    192.168.1.100
mail    IN    A    192.168.1.200

; CNAME records
ftp     IN    CNAME    www
Testing DNS Configuration:
nslookup
nslookup www.company.local 192.168.1.10
dig
dig @192.168.1.10 www.company.local
host
host www.company.local 192.168.1.10
Check Configuration Syntax
# Check main config
named-checkconf

# Check zone file
named-checkzone company.local /var/cache/bind/db.company.local
Service Management
# Reload configuration
systemctl reload bind9

# Check service status
systemctl status bind9

# View query log
tail -f /var/log/syslog | grep named

5. Dynamic Host Configuration Protocol (DHCP)

Apa itu DHCP?
  • Protokol untuk memberikan konfigurasi IP secara otomatis ke client
  • Menggunakan port 67 (server) dan 68 (client)
  • Menggunakan UDP broadcast untuk communication
  • Dynamic, automatic IP management untuk network devices
DHCP Benefits

Automatic IP Configuration

Centralized Management

Reduced Administration

DHCP Process (DORA):
Discover
→
Client mencari DHCP server
Offer
→
Server menawarkan IP address
Request
→
Client meminta IP yang ditawarkan
Acknowledge
Server mengkonfirmasi dan memberikan lease
Komponen DHCP:
Scope

Range IP addresses yang dapat diberikan

192.168.1.100-200
Lease

Durasi penggunaan IP oleh client

Default: 24 hours
Reservation

IP tetap untuk client tertentu

Based on MAC address
Options

Konfigurasi tambahan

Gateway, DNS, domain

6. DHCP Server di Linux

ISC DHCP Server Installation:
Ubuntu/Debian
# Install DHCP server
sudo apt update
sudo apt install isc-dhcp-server

# Configure interface
sudo nano /etc/default/isc-dhcp-server

# Set INTERFACESv4="eth0"
CentOS/RHEL
# Install DHCP server
sudo yum install dhcp

# atau dengan dnf
sudo dnf install dhcp-server

# Start service
sudo systemctl enable dhcpd
sudo systemctl start dhcpd
DHCP Server Configuration:
/etc/dhcp/dhcpd.conf
# Global options
option domain-name "company.local";
option domain-name-servers 192.168.1.10, 8.8.8.8;
default-lease-time 600;
max-lease-time 7200;
authoritative;

# Subnet declaration
subnet 192.168.1.0 netmask 255.255.255.0 {
  range 192.168.1.100 192.168.1.200;
  option routers 192.168.1.1;
  option subnet-mask 255.255.255.0;
  option broadcast-address 192.168.1.255;
}

# Fixed address for specific MAC
host printer {
  hardware ethernet 08:00:27:4a:5b:6c;
  fixed-address 192.168.1.50;
}
DHCP Management:
Monitoring DHCP Leases
# View current leases
cat /var/lib/dhcp/dhcpd.leases

# Monitor DHCP activity
tail -f /var/log/syslog | grep dhcp

# Check server status
systemctl status isc-dhcp-server
Configuration Testing
# Test configuration syntax
dhcpd -t

# Test with specific config file
dhcpd -cf /etc/dhcp/dhcpd.conf -t

# Debug mode
dhcpd -d

12. DNS Resolution Simulator

Interactive DNS Lookup Simulator
DNS Query:
Quick Tests:
Resolution Process:
Enter a domain and click "Perform DNS Lookup" to see the resolution process...
Query Results:
Results will appear here...

Ringkasan Pembelajaran

Pada pertemuan ini kita telah mempelajari konfigurasi dan manajemen DNS dan DHCP, dua layanan jaringan fundamental untuk infrastruktur IT modern.

Key Takeaways:
  • Pemahaman DNS hierarchy dan resolution process
  • Konfigurasi BIND9 DNS server di Linux
  • Setup ISC DHCP server untuk automatic IP assignment
  • Integrasi DNS dan DHCP dengan dynamic updates
Next Topic Preview:

Pertemuan berikutnya: Layanan SSH dan FTP - remote access dan file transfer yang aman.

Sebelumnya Selanjutnya: Bagian-2