Category: CCNA

Cisco Certified Network Associate certification resources

Diagram of link-state routing operation stages including establishing neighbor adjacencies with Hello packets, exchanging LSAs, building LSDB, creating SPF tree, and populating forwarding database.
CCNA August 31, 2019

Link State Operation – Exclusive Explanation (Updated 2025)

Link state routing protocols, such as OSPF and IS-IS, are fundamental in modern networks due to their efficiency and scalability. For CCNA and CCNP students, mastering link-state operations is crucial for exams and real-world troubleshooting. This article dives into how these protocols work, focusing on OSPF as the primary example. Unlike distance-vector protocols, link-state protocols...
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OSPF overview diagram with Edsger W. Dijkstra portrait and components including hardware, databases, routing protocol messages, and algorithm connected to central OSPF node.
CCNA August 31, 2019

Introduction to Open Shortest Path First (OSPF)

Open Shortest Path First (OSPF) is a link-state routing protocol replacing the distance vector routing protocol, RIP. RIP was acceptable in the early days of networking. RIP uses hop count as the metric, which does not work better in the larger network. Open Shortest Path First (OSPF) has many advantages over RIP. It can scale...
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Diagram illustrating route lookup and forwarding in a routing table with networks 172.16.0.0/16, 172.16.1.0/24, 172.16.2.0/24, and packet destination 172.16.2.100 sent to Ethernet1/1.
CCNA August 30, 2019

Best Route, Routing Table Terms, and Lookup Process (Updated 2025)

The best route is the longest match route to the destination IP address. The route lookup process matches the destination IP address with the available routes in the routing table and selects the longest-matched route as the forwarding route. To match the destination IPv4 address of a packet with the routes in the routing table,...
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Cisco routing table entry diagram with D code for EIGRP route to 182.168.0.0 network via Serial0/1/0.
CCNA August 30, 2019

What is the Routing Table Entries

The routers are typically responsible for directing traffic across multiple networks. Each router maintains a list of known networks and directions in its routing table. The router performs a routing table entries lookup to find the proper interface that leads to the destination address. Each entry in a routing table is called a “route entry:...
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Illustrated diagram of link-state routing protocol steps showing routers in discovery, hello protocol, LSP building, and flooding phases.
CCNA August 30, 2019

Link-State Routing Protocol

Link-state routing protocols are also known as shortest-path first protocols. They maintain a complete picture of all the routers running a link-state routing protocol in the complete network. All routers running a link-state routing protocol originate information about themselves and their directly connected routers, links, and the state of those links as multicast messages. The...
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Network topology diagram showing routers R1 to R6 with link costs and three paths totaling 59, 42, and 37 for SPF protocol example
CCNA August 29, 2019

Understanding the Shortest Path First (SPF) Protocol: Link-State Routing with Dijkstra’s Algorithm

In networking, efficient routing is crucial for data transmission across complex topologies. The Shortest Path First (SPF) Protocol, also known as Link-State Routing, uses Edsger Dijkstra’s SPF Algorithm to determine the optimal path for packets. Protocols like Open Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (IS-IS) are prime examples of link-state routing protocols. These...
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IPv6 RIPng network topology diagram showing interconnected Cisco routers
CCNA August 29, 2019

How to Advertise IPv6 Networks in RIPng

IPv6 Routing Information Protocol (RIP), also known as RIPng (RIP Next Generation), supports IPv6 addresses. It is a Distance Vector routing protocol that uses a hop count as a routing metric. After enabling IPv6 RIP, we also need to configure the advertisement of IPv6 RIP routes. We can display IPv6 RIP settings to verify the...
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Diagram showing RIP passive interface configuration with Router0 connected to a LAN and Router1, marking FastEthernet 0/1 as passive to stop updates, including configuration commands.
CCNA August 27, 2019

How to Configure RIP Passive Interface

By default, the Routing Information Protocol (RIP) sends routing table updates every 30 seconds on all enabled interfaces. In RIP version 1 (RIPv1), these are broadcasts to 255.255.255.255, while RIP version 2 (RIPv2) uses multicasts to 224.0.0.9. However, updates should only be sent on interfaces connected to other RIP-enabled routers to avoid unnecessary traffic. This...
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Diagram of Routing Information Protocol (RIP) network topology showing hop count metric, maximum 15 hops, and periodic route exchanges between routers connected via Ethernet interfaces to networks 192.168.1.0/24 and 192.168.2.0/24.
CCNA August 27, 2019

How to Configure Routing Information Protocol (RIP)

Routing Information Protocol (RIP) is a dynamic routing protocol that defines a way for routers to connect different networks using the Internet Protocol (IP) to share information about how to route traffic among these other networks. The Routing Information Protocol (RIP) uses hop count as a routing metric to determine the best path between the source and...
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