L10. Describe typical architectures and functions of a router. Flashcards
What is a router?
A networking device that connects multiple networks together, facilitating communication between devices across different network segments.
What are the components of a router?
Input port, output port, switching fabric, processor (CPU), memory (RAM)
What does the input port do?
- It terminates the incoming physical link to the router.
- It performs the data link layer functionality needed to interoperate with the data link layer functionality on the other side of the incoming link.
- It performs a lookup and forwarding function so that a datagram forwarded into the switching fabric of the router emerges at the appropriate output port.
What does the output port do?
- Stores packets received from the switching fabric
- Transmits the packets on the outgoing link by performing the link-layer and physical-layer functions (the reverse data link and physical layer functionality as the input port)
What does the switching fabric do?
It is the combination of hardware and software which forwards data coming in to a network node to the correct port of the next node in the network.
What does the processor do?
- Executes routing protocols
- Maintains routing information and forwarding tables
- Makes forwarding decisions
- Performs network management functions within the router; processes control plane functions, such as calculating best paths, exchanging routing information with neighboring routers, and updating routing tables based on network topology changes
What does the RAM do?
Stores the routing table and buffered data.
Describe router interfaces
Routers feature multiple physical interfaces, including Ethernet ports, serial ports, and WAN interfaces, to connect to different types of networks and devices. Each interface is configured with an IP address and subnet mask, enabling the router to participate in routing and forwarding packets between networks.
What are the functions of a router?
Packet Forwarding, Routing Protocol Support, Traffic Filtering and Access Control, Network Address Translation (NAT), Quality of Service (QoS)
What is packet forwarding?
Sending packets between networks based on destination IP addresses, using routing tables to determine the optimal path.
How does a router forward a packet?
Upon receiving a packet, the router examines the destination IP address, performs a lookup in its routing table, and forwards the packet out the appropriate interface towards its destination.
What is routing protocol support?
The support for various routing protocols, such as RIP (Routing Information Protocol), OSPF (Open Shortest Path First), BGP (Border Gateway Protocol), and EIGRP (Enhanced Interior Gateway Routing Protocol), to exchange routing information with neighboring routers and maintain up-to-date routing tables. These protocols enable routers to dynamically learn network topologies, calculate optimal paths, and adapt to changes in network conditions.
What is traffic filtering and access control?
Routers can enforce access control policies and filter traffic based on criteria such as source/destination IP addresses, port numbers, and protocol types. Access Control Lists (ACLs) are commonly used to define filtering rules that permit or deny specific types of traffic, providing security and traffic management capabilities.
What is NAT?
Network Address Translation (NAT) can be performed by routers to translate IP addresses between different network domains. NAT allows private IP addresses used within a local network to be translated into a single public IP address when accessing the internet, conserving public IP address space and enhancing network security.
What is QoS?
Quality of Service (QoS) mechanisms are used by routers to prioritize and manage network traffic based on predefined policies. QoS features enable routers to allocate bandwidth, prioritize critical applications, and enforce service-level agreements (SLAs) to ensure optimal network performance and user experience.
