1|Page
WGU D413 EXAM 2026/2027 |
TELECOMMUNICATIONS FUNDAMENTALS 300
MULTIPLE CHOICE QUESTIONS WITH
ANSWERS & DETAILED RATIONALES HIGH-
YIELD TEST BANK – FIRST ATTEMPT
GUARANTEE
---
## Table of Contents
| Domain | Topic | Question Numbers | Page |
|--------|-------|------------------|------|
| **Domain 1** | OSI Model & Encapsulation | 1 – 40 | 3 |
| **Domain 2** | TCP/IP Suite & Common Protocols | 41 – 90 | 8 |
| **Domain 3** | IP Addressing & Subnetting (IPv4) | 91 – 150 | 14 |
| **Domain 4** | Routing Fundamentals & Protocols | 151 – 190 | 21 |
| **Domain 5** | Switching & VLANs | 191 – 220 | 26 |
| **Domain 6** | Wireless Networking (802.11) | 221 – 240 | 30 |
| **Domain 7** | Network Security Fundamentals | 241 – 270 | 34 |
| **Domain 8** | Network Troubleshooting & Tools | 271 – 300 | 38 |
,2|Page
| **Bonus** | 20 Rapid-Fire Memory Facts | 301 – 320 | 42 |
---
# DOMAIN 1: OSI MODEL & ENCAPSULATION (Questions 1–40)
**Question 1**
Which layer of the OSI model is responsible for logical addressing and
path determination?
A) Data Link Layer
B) Network Layer
C) Transport Layer
D) Session Layer
**Answer:** B) Network Layer
**Rationale:** The Network Layer (Layer 3) handles logical addressing
(IP addresses) and routing decisions. The Data Link Layer (Layer 2)
uses MAC addresses. Transport Layer (Layer 4) handles segmentation
and error recovery.
---
,3|Page
**Question 2**
A router receives a frame, decapsulates it, and forwards the packet out
another interface. What happens to the source and destination MAC
addresses?
A) Both remain the same
B) Source MAC becomes the router's, destination MAC becomes next
hop
C) Both are stripped and never replaced
D) Source MAC becomes the destination MAC
**Answer:** B) Source MAC becomes the router's, destination MAC
becomes next hop
**Rationale:** Each time a packet crosses a router, the Layer 2 frame is
rebuilt. The source MAC becomes the outgoing router interface's MAC,
and the destination MAC becomes the next hop device's MAC. IP
addresses (Layer 3) remain unchanged unless NAT is involved.
---
**Question 3**
At which OSI layer does a traditional switch primarily operate?
A) Layer 1
B) Layer 2
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C) Layer 3
D) Layer 4
**Answer:** B) Layer 2
**Rationale:** Traditional switches forward frames based on MAC
addresses, which are Layer 2 identifiers. Some "Layer 3 switches" can
also route, but for WGU D413 fundamentals, a switch = Layer 2.
---
**Question 4**
What is the PDU (Protocol Data Unit) called at the Transport Layer?
A) Frame
B) Packet
C) Segment
D) Bit
**Answer:** C) Segment
**Rationale:** Layer 4 (Transport) → Segment (TCP) or Datagram
(UDP). Layer 3 (Network) → Packet. Layer 2 (Data Link) → Frame.
Layer 1 (Physical) → Bits.
WGU D413 EXAM 2026/2027 |
TELECOMMUNICATIONS FUNDAMENTALS 300
MULTIPLE CHOICE QUESTIONS WITH
ANSWERS & DETAILED RATIONALES HIGH-
YIELD TEST BANK – FIRST ATTEMPT
GUARANTEE
---
## Table of Contents
| Domain | Topic | Question Numbers | Page |
|--------|-------|------------------|------|
| **Domain 1** | OSI Model & Encapsulation | 1 – 40 | 3 |
| **Domain 2** | TCP/IP Suite & Common Protocols | 41 – 90 | 8 |
| **Domain 3** | IP Addressing & Subnetting (IPv4) | 91 – 150 | 14 |
| **Domain 4** | Routing Fundamentals & Protocols | 151 – 190 | 21 |
| **Domain 5** | Switching & VLANs | 191 – 220 | 26 |
| **Domain 6** | Wireless Networking (802.11) | 221 – 240 | 30 |
| **Domain 7** | Network Security Fundamentals | 241 – 270 | 34 |
| **Domain 8** | Network Troubleshooting & Tools | 271 – 300 | 38 |
,2|Page
| **Bonus** | 20 Rapid-Fire Memory Facts | 301 – 320 | 42 |
---
# DOMAIN 1: OSI MODEL & ENCAPSULATION (Questions 1–40)
**Question 1**
Which layer of the OSI model is responsible for logical addressing and
path determination?
A) Data Link Layer
B) Network Layer
C) Transport Layer
D) Session Layer
**Answer:** B) Network Layer
**Rationale:** The Network Layer (Layer 3) handles logical addressing
(IP addresses) and routing decisions. The Data Link Layer (Layer 2)
uses MAC addresses. Transport Layer (Layer 4) handles segmentation
and error recovery.
---
,3|Page
**Question 2**
A router receives a frame, decapsulates it, and forwards the packet out
another interface. What happens to the source and destination MAC
addresses?
A) Both remain the same
B) Source MAC becomes the router's, destination MAC becomes next
hop
C) Both are stripped and never replaced
D) Source MAC becomes the destination MAC
**Answer:** B) Source MAC becomes the router's, destination MAC
becomes next hop
**Rationale:** Each time a packet crosses a router, the Layer 2 frame is
rebuilt. The source MAC becomes the outgoing router interface's MAC,
and the destination MAC becomes the next hop device's MAC. IP
addresses (Layer 3) remain unchanged unless NAT is involved.
---
**Question 3**
At which OSI layer does a traditional switch primarily operate?
A) Layer 1
B) Layer 2
, 4|Page
C) Layer 3
D) Layer 4
**Answer:** B) Layer 2
**Rationale:** Traditional switches forward frames based on MAC
addresses, which are Layer 2 identifiers. Some "Layer 3 switches" can
also route, but for WGU D413 fundamentals, a switch = Layer 2.
---
**Question 4**
What is the PDU (Protocol Data Unit) called at the Transport Layer?
A) Frame
B) Packet
C) Segment
D) Bit
**Answer:** C) Segment
**Rationale:** Layer 4 (Transport) → Segment (TCP) or Datagram
(UDP). Layer 3 (Network) → Packet. Layer 2 (Data Link) → Frame.
Layer 1 (Physical) → Bits.
