Introduction to Computer Networking, Architectures, and Topologies

1. Secure SNMP Protocol

• Use only SNMPv3 (older versions are vulnerable to interception)
• Enable authentication and encryption using TSM or USM models

2. Protect IPv6 Advertisements with RA Guard

• Use RA Guard to filter spoofed Router Advertisement messages
• Allow only valid RA messages to reach the network

3. Port Security

• Restrict access based on approved MAC addresses
• Disable unused switch ports to block rogue devices

4. Detect and Block Spoofed ARP with DAI

• Enable DHCP Snooping and Dynamic ARP Inspection (DAI)
• Validate IP-to-MAC bindings and drop fraudulent ARP frames

5. Private VLANs

• Use "Community" and "Isolated" VLANs to logically separate devices
• Limit traffic visibility among hosts within the same subnet

6. Disable Unused Ports and Services

• Turn off unnecessary ports and protocols (e.g., Telnet, SNMPv1/v2)
• Reduce surface area for attacks and misconfigurations

7. Password and Default Account Management

• Rename or disable default accounts
• Enforce strong password policies (minimum 8 characters with complexity)

8. Perform Security Audits

• Conduct walk-throughs, inspect physical spaces, and train users
• Identify deviations from policy and correct vulnerabilities

9. Enable DHCP Snooping

• Prevent rogue DHCP servers by establishing trusted ports
• Build binding tables to validate legitimate DHCP traffic

10. Change Default VLAN

• Assign switch ports to non-default VLANs (e.g., VLAN10)
• Avoid misuse of default VLAN1 for production systems

11. Patch Firmware and Drivers Regularly

• Install updates on a regular schedule
• Test updates in a staging environment before deployment

12. Apply ACLs and Role-Based Access Control (RBAC)

• Use Access Control Lists to permit/deny traffic based on IP
• Define roles and assign limited privileges to job-specific groups

13. Harden Firewall Rules

• Apply implicit deny: only allow explicitly authorized traffic
• Ensure firewall rules are precise and validated

14. Wireless Network Security

• Use MAC filtering for small networks
• Isolate guest and client devices from the main network
• Lower AP transmit power and use directional antennas
• Deploy strong PSK or EAP-TLS with digital certificates and RADIUS server

15. IoT Security Best Practices

• Place IoT devices in separate VLANs
• Enable IDS/IPS for monitoring and blocking IoT-based botnets or exploits

📋 Hardening Quick Reference Table

Technique	Main Objective	Suggested Actions
SNMPv3	Secure management traffic	Enable TSM/USM encryption & auth
RA Guard	Block spoofed IPv6 ads	Filter invalid RA messages
Port Security	Restrict switch port access	MAC locking, disable unused ports
ARP Inspection	Prevent ARP spoofing	Enable DHCP Snooping + DAI
Private VLANs	Logical device isolation	Configure Community/Isolated VLANs
DHCP Snooping	Block rogue DHCP servers	Trusted ports + binding table
ACL / RBAC	Traffic and access control	IP ACLs and role-based privileges
Wireless Security	Protect wireless connectivity	Strong PSK, EAP, isolation, MAC filters
IoT Security	Segmentation and monitoring	Dedicated VLAN, enable IDS/IPS