CCST Basic Routing and Switching 2 — Questions and Answers
Question 1: What is the primary purpose of a default gateway in a network?
- To assign IP addresses to devices
- To forward traffic destined for networks outside the local subnet (Correct answer)
- To filter incoming traffic based on MAC addresses
- To provide DNS resolution services
Correct answer: To forward traffic destined for networks outside the local subnet
A default gateway forwards packets destined for networks not on the local subnet.
The default gateway is a router interface on the same subnet as the sending device. When a host generates traffic for a destination IP outside its local network, it compares the destination against its subnet mask. If remote, the host forwards the frame to the default gateway's MAC address for routing.
Question 2: Which command displays the routing table on a Cisco router?
- show arp
- show ip route (Correct answer)
- show interfaces
- show mac-address-table
Correct answer: show ip route
The 'show ip route' command displays the complete IP routing table including connected, static, and dynamic routes.
The 'show ip route' command is one of the most frequently used troubleshooting commands. It displays routes organized by protocol (C for connected, S for static, O for OSPF), along with next-hop addresses, outgoing interfaces, and administrative distance/metric.
Question 3: What does a Layer 2 switch use to make forwarding decisions?
- IP addresses
- MAC addresses (Correct answer)
- Port numbers
- Routing protocols
Correct answer: MAC addresses
Layer 2 switches use MAC addresses stored in a CAM table to forward frames to the correct port.
A Layer 2 switch examines the destination MAC address in each incoming Ethernet frame and looks it up in its MAC address table. If found, the switch forwards the frame only to that port. If unknown, it floods the frame out all ports except the source port.
Question 4: What is the administrative distance of a directly connected route?
- 0 (Correct answer)
- 1
- 5
- 110
Correct answer: 0
Directly connected routes have an administrative distance of 0, the most trustworthy value.
Administrative distance (AD) ranks routing information trustworthiness from 0 to 255. Directly connected = 0, static = 1, OSPF = 110, RIP = 120. When multiple sources provide paths to the same destination, the lowest AD wins.
Question 5: Which switching method examines only the destination MAC address before forwarding a frame?
- Store-and-forward
- Cut-through (Correct answer)
- Fragment-free
- Adaptive switching
Correct answer: Cut-through
Cut-through switching reads only the first 6 bytes (destination MAC) before forwarding, providing lowest latency but no error checking.
Cut-through switching begins forwarding as soon as it reads the destination MAC. Store-and-forward waits for the entire frame and checks CRC. Fragment-free reads the first 64 bytes to filter collision fragments.
Question 6: What is the purpose of the ARP protocol in networking?
- To translate domain names to IP addresses
- To resolve IP addresses to MAC addresses (Correct answer)
- To assign IP addresses dynamically
- To encrypt data during transmission
Correct answer: To resolve IP addresses to MAC addresses
ARP resolves a known IP address to an unknown MAC address on the local network segment for Layer 2 frame delivery.
ARP sends a broadcast request asking 'Who has IP X.X.X.X?' The device with that IP responds with its MAC address. The mapping is cached in the ARP table for future use.
CCST Basic Routing and Switching 2
What is the primary purpose of a default gateway in a network?