CCNA
Cisco Certified Network Associate certification resources
How to OSPF MD5 Authentication
OSPF supports routing protocol authentication using MD5 Authentication. It is more secure than plain text authentication. It uses the MD5 algorithm to calculate a hash value from the contents of the OSPF packet and a password and then the hash value is transmitted in the packet. The receiver side, which knows the password, calculates its...
Introduction to OSPF Authentication
An attacker with a laptop and a copy of Wireshark can inject false LSAs into an OSPF domain in under 30 seconds if the network uses null authentication. This is not a theoretical attack. A 2024 SANS survey found that 38% of enterprise OSPF deployments still run with no authentication configured, despite RFC 5709 and...
OSPF Hello and Dead Intervals – Exclusive Details
Devices enable OSPF to constantly track the status of their neighbors, sending and receiving hello packets. Hello, packets show whether each neighbour still is functioning, and sending and receiving link-state advertisement and acknowledgment packets. OSPF sends hello packets and expects to receive Hello packets at particular intervals. The Hello and Dead Intervals timer is included...
Propagating a Default Static Route in OSPF
We have already discussed the Default route Propagation in “Propagate Default Route in RIP”. In this article, I am going to discuss propagating a default static route in OSPFv2 and OSPFv3. The route propagation is useful when there is a single exit point in the network to reach the internet or any other service. The...
OSPF Priority: DR/BDR Election, Configuration, and Verification
Each broadcast and Non-Broadcast Multi-Access (NBMA) network has a designated router. This router is the central point for collecting and distributing LSAs (Link-State Advertisements), so it must have enough CPU and memory capability to handle the workload. The OSPF priority value is the primary mechanism for controlling which router wins the DR/BDR election on these...
What is OSPF Designated Router
In the previous lesson, we discussed the challenges of the OSPF Multi-access network. The two challenges are unwanted adjacencies and the flooding of LSAs. The solution is the Designated Router (DR). DRs are designated to coordinate topology updates. On multiaccess networks, at initialization, a Designated Router (DR) and a backup designated router (BDR) are elected....
Frame Control Field Format – Exclusive Explanation
We have already discussed the frame control field format in the previous lesson that the Frame Control field contains multiple subfields. The figure below illustrates the subfields of the frame control field. Protocol Version – It is a 2-bit field that indicates the current version of the protocol. The receiving devices use this value to...
What is Wireless 802.11 Frame
All Layer 2 frames contain a header, payload, and FCS section. The 802.11 frame format is similar to the Ethernet frame format, with the exception that it contains more fields. The figure below illustrates the wireless 802.11 frame formats and fields. Frame Control – It is 2 bytes long field which determines the type of wireless...
Types of OSPF Network – Introduction
OSPF is a dynamic link-state routing protocol replacing the distance vector routing protocol, RIP. However, OSPF has important advantages over RIP. OSPF offers faster convergence and scales to much larger network implementations. The OSPF defines five types of OSPF networks: Point-to-point—A point–to–point network is when two routers are interconnected over a common link without any...
Introduction to Wireless Antennas
Wireless antennas are elements of a radio communications system that radiate and/or collect radiofrequency energy. They are usually connected using a low-loss coaxial cable to a power amplifier, splitter, and filter or directly to wireless devices. For outdoor usage, wireless antennas are often attached via mounting clamps to a mast or the side of a...