Cisco CCNA (200-301): IP Services
Table of Contents
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IP Services is 10% of the Cisco CCNA (200-301) exam. This module covers the services that make a network usable and manageable. These features show up constantly in real networks even though the domain weight is small.
These services translate addresses, keep time, hand out configuration, and report what the network is doing. You configure and verify each one.
Network Address Translation
NAT maps private addresses to public ones so internal hosts reach the internet. Static NAT maps one inside address to one outside address, a pool maps many to many, and PAT (overload) maps many private hosts to one public address with port numbers.
! Inside source NAT with a pool
Router(config)# ip nat pool POOL1 203.0.113.10 203.0.113.20 netmask 255.255.255.0
Router(config)# ip nat inside source list 1 pool POOL1
Router(config)# interface g0/0
Router(config-if)# ip nat inside
Verify translations with show ip nat translations.
DHCP, DNS, and NTP
| Service | Role |
|---|---|
| DHCP | Assigns IP, mask, gateway, and DNS to clients |
| DNS | Resolves names to IP addresses |
| NTP | Synchronizes clocks across devices |
A DHCP relay (ip helper-address) forwards requests when the server sits on another subnet. Accurate NTP time matters, because logs and certificates depend on it.
! Point an interface to a DHCP server on another subnet
Router(config-if)# ip helper-address 10.10.10.5
! Sync to an NTP server
Router(config)# ntp server 10.10.10.6
Management and Logging
SNMP polls device health and sends traps for events. Syslog records messages by facility and severity level.
| Level | Keyword |
|---|---|
| 0 | Emergency |
| 3 | Error |
| 6 | Informational |
| 7 | Debugging |
Lower numbers are more severe, so a level 0 message needs immediate attention.
Secure Remote Access
You manage devices remotely with SSH, which encrypts the session. Avoid Telnet, since it sends credentials in clear text. TFTP and FTP move configuration files and IOS images, with FTP supporting authentication.
! Enable SSH access
Router(config)# hostname R1
R1(config)# ip domain-name example.com
R1(config)# crypto key generate rsa modulus 2048
R1(config)# line vty 0 4
R1(config-line)# transport input ssh
Quality of Service
Per-hop behavior (PHB) decides how each device treats a packet. The steps are classification, marking, queuing, congestion management, policing, and shaping. Policing drops or remarks traffic over a limit, while shaping buffers it to smooth bursts. This keeps voice and video usable when links fill.
Next Steps
Secure these services in Security Fundamentals and automate them in Automation and Programmability . Review routing in IP Connectivity and return to the Cisco CCNA Course .
