Cisco CCNA (200-301)Network FundamentalsEasy
A small office network uses a single Cisco router for all routing functions. The router has two interfaces: GigabitEthernet0/0 connected to the internal LAN (192.168.1.0/24) and GigabitEthernet0/1 connected to the ISP's network for internet access (DHCP assigned). Which of the following statements about this router's function is most accurate?
- AThe router primarily functions as a wireless access point, providing Wi-Fi to the office.
- BThe router acts as a Layer 2 switch, forwarding frames between the LAN and ISP.
- CThe router is a firewall, inspecting all incoming and outgoing packets for security threats.
- DThe router performs Layer 3 forwarding, routing IP packets between different IP subnets.
Show answer & explanationAnswer & explanation
Correct answer: D. The router performs Layer 3 forwarding, routing IP packets between different IP subnets.
Routers operate at Layer 3 of the OSI model and are primarily responsible for forwarding IP packets between different IP networks (subnets). In this scenario, it connects the internal 192.168.1.0/24 subnet to the ISP's network, which is a different IP subnet.
Why the other options are wrong
- A. While some routers have integrated AP functionality, the primary function of a router described here is routing, not wireless access.
- B. Layer 2 switches forward frames within the same subnet; routers forward packets between different subnets.
- C. While many routers include firewall capabilities, its fundamental role in connecting different IP subnets is routing, not exclusively security.
Router Function (Layer 3)
A router is a network device that operates at Layer 3 (Network Layer) of the OSI model, primarily responsible for forwarding IP packets between different IP networks (subnets).
- Connects different broadcast domains and IP subnets.
- Uses IP addresses to make forwarding decisions.
- Maintains a routing table to determine the best path for packets.
- Prevents broadcast storms from propagating across networks.
Memory trick: Routers Route between Networks, Switches Switch within.