CCNA Chapter 5: Security Fundamentals (Advanced)

Device Security

Securing network devices like routers and switches is the first line of defense. Configurations include setting strong passwords, enabling SSH access, and using role-based CLI views.

Router(config)# line vty 0 4
Router(config-line)# password cisco
Router(config-line)# login
Device Security Diagram View Full Image

Port Security

Port Security prevents unauthorized access by limiting which MAC addresses can connect to a switch port. Violation modes include protect, restrict, and shutdown.

Switch(config-if)# switchport port-security
Switch(config-if)# switchport port-security maximum 2
Switch(config-if)# switchport port-security violation shutdown
Switch(config-if)# switchport port-security mac-address sticky
⚠️ Note: Sticky MAC learning allows a switch to dynamically learn MACs and convert them into static entries.
Port Security View Full Image

Access Control Lists (ACLs)

ACLs are used to filter traffic based on IP addresses, protocols, or ports. Standard ACLs filter only by source IP, while Extended ACLs allow filtering by source, destination, and protocol.

Router(config)# access-list 10 permit 192.168.1.0 0.0.0.255
Router(config)# interface fa0/0
Router(config-if)# ip access-group 10 in
📘 Tip: Place Standard ACLs near the destination, and Extended ACLs near the source.
ACL Diagram View Full Image

VPNs (Virtual Private Networks)

VPNs encrypt traffic over untrusted networks like the internet. Site-to-site VPNs use IPsec, while remote access VPNs commonly use SSL or IPsec with client software.

crypto isakmp policy 10
 encr aes
 hash sha
 authentication pre-share
 group 2
 lifetime 86400
✅ Real-World Insight: IPsec VPNs offer secure tunneling with confidentiality, integrity, and authentication using ESP and AH.
VPN Diagram View Full Image

Summary Table

Concept Description
Device Security Control access to network hardware through secure configurations
Port Security Limit access to switch ports using MAC filtering and violation actions
ACLs Filter traffic based on IP, protocol, and port rules
VPNs Encrypt and secure traffic over public networks
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