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GK One-Line Question & Answer

15541+ short questions with short answers, covering every category and sub-category on the site — no long articles to scroll through. Good for a fast recap before an exam, or a few minutes of daily practice.

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Computer Networks → Introduction to Computer Networks 32

What is DMVPN Phase 3
Hierarchical with summarization and shortcut switching
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What is FlexVPN
Cisco unified VPN framework based on IKEv2
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What is IKEv2 advantage over IKEv1
Simpler fewer messages faster and more secure
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What is MOBIKE in IKEv2
IKEv2 extension for mobility and multihoming
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What is RADIUS change of authorization (CoA)
Dynamically changing session attributes mid-session
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What is 802.1X EAPOL
EAP over LAN encapsulation for 802.1X
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What is MAB (MAC Authentication Bypass)
Authenticating devices by MAC address for non-802.1X devices
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What is WebAuth in network access
Browser-based authentication via captive portal
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What is IBNS 2.0 in Cisco
Identity-Based Networking Services framework
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What is Cisco ISE
Identity Services Engine for network access control
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What is profiling in NAC
Identifying device type and OS for policy application
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What is posture assessment in NAC
Checking device compliance before granting access
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What is ACL in network security
Rules filtering traffic based on various criteria
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What is PACL (Port ACL)
ACL applied directly to switch port
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What is RACL (Router ACL)
ACL applied on routed interface
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What is CoPP (Control Plane Policing)
Rate-limiting traffic destined to router control plane
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What is CPPr (Control Plane Protection)
Cisco feature for granular control plane traffic protection
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What is uRPF (Unicast Reverse Path Forwarding)
Anti-spoofing feature verifying source IP via routing table
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What is uRPF strict mode
Source IP must match interface it arrived on
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What is uRPF loose mode
Source IP must have route in routing table
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What is sinkholing in security
Redirecting malicious traffic to controlled analysis system
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What is TTL-based traceroute vs timestamp-based
Standard traceroute uses TTL ICMP uses timestamp option
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What is Paris-traceroute advantage
Uses flow-consistent probes for accurate ECMP path discovery
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What is MTR continuous traceroute advantage
Shows real-time packet loss and latency per hop continuously
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What is PMTUD black hole
ICMP fragmentation needed messages being blocked causing failure
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What is MPLS MTU consideration
MPLS labels add 4 bytes each requiring larger interface MTU
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What is jumbo frame benefit in data center
Reduces CPU overhead for large data transfers
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What is baby giant issue
Frames slightly over 1518 bytes causing drops on strict interfaces
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What is PFC (Priority Flow Control) in DCB
Per-priority flow control for lossless data center Ethernet
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What is DCB (Data Center Bridging)
Set of IEEE enhancements for lossless data center Ethernet
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What is DCBX
Data Center Bridging Capability Exchange protocol
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What is ETS (Enhanced Transmission Selection) in DCB
Bandwidth allocation across traffic classes
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Computer Networks → Switching Techniques 4

What is guest VLAN in 802.1X
Limited access VLAN for unauthenticated users
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What is auth-fail VLAN in 802.1X
Restricted VLAN for failed authentication attempts
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What is critical VLAN in 802.1X
VLAN used when RADIUS server is unreachable
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What is VACL (VLAN ACL)
ACL filtering traffic within or between VLANs
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Computer Networks → Transport Layer 2

What is TCP MSS clamping
Adjusting MSS in SYN to prevent fragmentation issues
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What is QCN (Quantized Congestion Notification)
End-to-end congestion notification for lossless Ethernet
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Computer Networks → Data Link Layer 2

What is Ethernet pause frame (802.3x)
Flow control mechanism requesting transmitter to pause
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What is FCoE (Fiber Channel over Ethernet)
Running Fiber Channel SAN traffic over Ethernet
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