NE Cheat Sheet 2026

The 30 highest-yield NE facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which feature prevents traffic from being forwarded from one access port to another on the same VLAN, enhancing security? → Private VLAN (PVLAN) / Protected Ports
2. A user cannot access a remote server but can ping the default gateway. What is the most likely issue? → Routing or firewall issue between the user's network and the server's network
3. What distinguishes a Type 2 hypervisor from a Type 1 hypervisor in a virtualized network environment? → Type 2 runs on top of a host operating system rather than directly on hardware
4. Which type of ACL can filter traffic based on both source and destination IP addresses and port numbers? → Extended ACL
5. What is the role of a CPE (Customer Premises Equipment) in a WAN service? → Hardware owned by the ISP placed at the customer site to terminate the WAN circuit
6. What is the primary advantage of SD-WAN over traditional WAN technologies? → It provides centralized management and dynamic path selection across multiple WAN links
7. What is a Switched Virtual Interface (SVI) on a Layer 3 switch? → A virtual interface associated with a VLAN used for inter-VLAN routing and management
8. Which command verifies end-to-end IP reachability between two hosts? → ping
9. What is the VNI (VXLAN Network Identifier) used for in a VXLAN deployment? → Uniquely identifying a VXLAN segment, similar in concept to a VLAN ID
10. Which protocol is most commonly used as the control plane for VXLAN in modern data center deployments? → BGP EVPN
11. What is the difference between static and dynamic routing? → Static routing requires manual updates, while dynamic routing updates automatically
12. What is the primary purpose of GRE (Generic Routing Encapsulation) in network virtualization? → To encapsulate a wide variety of network layer protocols inside IP tunnels
13. What does syslog provide in a network management context? → Centralized logging of device events and alerts for auditing and troubleshooting
14. What is the default port cost for a 1 Gbps link in IEEE 802.1D Spanning Tree Protocol? → 19
15. What does EVPN (Ethernet VPN) provide in a VXLAN-based network virtualization environment? → A BGP-based control plane for distributing MAC and IP reachability information
16. Which type of malware disguises itself as legitimate software but performs malicious actions when executed? → Trojan horse
17. What is the function of an Intrusion Prevention System (IPS) compared to an IDS? → IPS actively blocks malicious traffic; IDS only detects and alerts
18. What is the primary purpose of network flow analysis tools like SolarWinds NTA or ntopng? → To identify top talkers, unusual traffic patterns, and bandwidth hogs using flow data
19. Which attack involves sending crafted DHCP responses to clients in an attempt to become their default gateway? → DHCP spoofing
20. Which metric does MPLS Traffic Engineering (TE) use to calculate constrained paths across the network? → Bandwidth, delay, and administrative constraints via RSVP-TE or OSPF-TE extensions
21. What is the primary security benefit of network segmentation using VLANs? → It limits the blast radius of a breach by containing threats within a segment
22. What does RSTP (802.1w) provide compared to traditional STP (802.1D)? → Faster convergence by introducing new port roles and states
23. What does an 'administratively down' interface status indicate on a Cisco device? → The interface has been manually shut down with the 'shutdown' command
24. What does the 'show mac address-table' command display on a Cisco switch? → Dynamically learned and static MAC-to-port mappings
25. In the context of WAN SLAs, what does jitter measure? → Variation in packet delay over time
26. What does the term 'zero-day vulnerability' mean? → A vulnerability that is publicly known but has no vendor patch yet
27. Which type of hypervisor runs directly on physical hardware without requiring a host operating system? → Type 1 hypervisor
28. Which command shows the current ARP cache on a Cisco router? → show arp
29. What does the term "SSID" stand for in wireless networking? → Service Set Identifier
30. What is the primary function of a router in a network? → To route data packets between different networks