CCNA Chapter 4: IP Services

DHCP (Dynamic Host Configuration Protocol)

DHCP automates IP address assignment, reducing manual configuration. It uses the DORA process: Discover, Offer, Request, Acknowledge.

Exam Tip: Ensure devices receive the correct gateway and DNS with DHCP options.
Router(config)# ip dhcp pool SALES
Router(dhcp-config)# network 192.168.10.0 255.255.255.0
Router(dhcp-config)# default-router 192.168.10.1
Router(dhcp-config)# dns-server 8.8.8.8
DHCP DORA Process View Full Image

DNS (Domain Name System)

DNS translates human-friendly domain names into IP addresses. This service is essential for internet browsing and service discovery.

Security Note: DNS spoofing can mislead users to fake websites.
Router(config)# ip name-server 8.8.8.8
DNS Resolution View Full Image

NAT (Network Address Translation)

NAT allows private IP addresses to communicate with the internet by translating them to a public IP. Three types exist: Static, Dynamic, and PAT (Port Address Translation).

Real-World Tip: PAT conserves IP addresses and is the most common in home and office networks.
ip nat inside source list 1 interface g0/1 overload
access-list 1 permit 192.168.0.0 0.0.0.255
NAT Translation View Full Image

QoS (Quality of Service)

QoS manages bandwidth by prioritizing traffic like voice and video. It ensures critical applications perform well during congestion.

class-map VOICE
 match ip dscp ef
policy-map QOS-POLICY
 class VOICE
  priority 512
interface g0/1
 service-policy output QOS-POLICY
Quick Fact: DSCP EF (Expedited Forwarding) is commonly used for voice traffic.

NTP (Network Time Protocol)

NTP synchronizes device clocks over a network. Accurate time is critical for logs, certificates, and troubleshooting.

Router(config)# ntp server 192.168.1.100
Router(config)# clock timezone MYT 8
NTP Synchronization View Full Image

Summary Table

Service Description
DHCP Automatically assigns IP configuration to clients
DNS Resolves domain names to IP addresses
NAT Translates private IPs to public for internet access
QoS Prioritizes traffic to manage bandwidth and reduce latency
NTP Synchronizes time across network devices
Back to Home