Ethernet

Ethernet is a system that links the computers within a local area which consists of #hardware (e.g. network interface card), software, and cabling for the connections. Computers are attached to the Ethernet with a shared #data link. It supports network speed ranging from 10Mbps to 10Gbps. It is the most dominated protocol for the #Local-Area Network (LAN) communication.

Ethernet uses the Carrier Sense Multiple Access Collision Detect Protocol (CSMA/CD)# to resolve collisions. Further reduction of the occurrence of the collision can be done by dividing the network into Collision Domain#.

It uses transparent bridging# where forwarding decisions happen one hop (or network segment) at a time.

Using Switch# can greatly improve the network throughput (bandwidth) by configure the port connected to the Ethernet as full duplex (two-way communications, simultaneously receive incoming traffic and transmit traffic).

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Static Routing

In #Cisco Internetwork Operating System (IOS), this could be done using the command ip route and supply it with the destination network address, its subnet mask and the next-hop router’s IP address or the outgoing interface (called exit interface). Since using next-hop router’s IP address for static route could result in Recursive Route Lookup#, it is advised to use exit interface when ever possible. However, in the case of configuring on an Ethernet# link, the best practice is to configure with both the next-hop router’s IP address and the exit interface to avoid Address Resolution Protocol (ARP)# shenanigans.
Router

Both its Ethernet# and serial interface (e.g., HWIC-2T) could be assigned with #IP Address. Before adding the interface modules to the router, the best practice is to turn off the router if it is running and then switch it on after the installation. It is same in Cisco Packet Tracer environment.

Router consists of two types of interfaces: LAN interfaces and WAN interfaces. LAN interfaces could be used to connect Router to the LAN which is typically connected with an RJ-45 jack (Unshielded Twisted Pair Cable (UTP)). For connecting Router to Switch, we use a Straight-Through Cable. In the case of Router to Router, we use a Crossover Cable. For PC to Router, we will use Roll-Over Cable. LAN interface could serve Ethernet# and Fast Ethernet.
Optical Ethernet

Optical Ethernet utilises Gigabit Interface Converter (GBIC) in order to convert an #Ethernet stream to an optical signal. It is currently the simplest and cheapest form of #optical transport.
Network Interface Card (NIC)

NIC is a piece of hardware which connect a device to the network and assigned its host with an #IP Address. There are two kinds of NICs: Ethernet# NIC for wired connection and WLAN for wireless connection.
Local-Area Network (LAN)

Ethernet#
Link-State Routing Protocol

In Link-State Routing, aka Shortest Path First (SPF), each #Router needs to know the entire topology of the network with the aid of a database. The database stores link states, that is information about the state of a router’s links, which include IP Address, type of network (Ethernet or serial point-to-point link), cost, and neighbours. This database will be identical to all routers using the same protocol albeit processed independently. The #exchange of topology information (called flooding) only happened upon the initial set-up of the network and when there is a topological change in the network (new router added or router is removed). Since only information specific to the change needs to be propagated, combined with the hierarchical model used by the protocol, it limits the scope of the route changes that occur and provides better scaling than Distance Vector Routing Protocol. Though there still a need for keep alive message between router and its neighbours to detect potential topological changes.
IP Address

Some interfaces, such as Network Interface Card (NIC)# and Router’s# Ethernet or serial interface, are could be assigned with an IP Address.
IEEE 802.1Q

IEEE 802.1Q is an efficient #VLAN Trunking technique introduced by Institute of Electrical and Electronic Engineers (IEEE)#. It only inserts 4 bytes to the Ethernet# frame.
Ethernet Hub

Ethernet Hub is a #202207051821 operates at 202206131647# which enable devices to be plugged in or out without disturbing the #202207051550 network. Its ports also function as a 202207051832. Since it doesn’t have the information of the network topology, it will simply propagate the received package to every other port, which raises security concerns and wastes bandwidth.
Data Link Layer

Ethernet#
Cisco OSPF Router Configuration

The default OSPF cost in Cisco routers is using a reference bandwidth, usually \(10^8\) over the default bandwidth of the interface. However, with the default value of the reference bandwidth, the cost of travelling in 10 Gigabit Ethernet#, Gigabit Ethernet and Fast Ethernet will be the same which is not true. We can change it with the command auto-cost reference-bandwidth {integer} where the integer is in Mb/s. ip ospf cost {integer} can be used to manually adjust the cost of an interface in the Interface Configuration.
Carrier Sense Multiple Access Collision Detect Protocol (CSMA/CD)

CSMA/CD is an #202207051550 protocol aimed to resolve collisions between computers when sharing the #data link. It defines how a computer should listen to the network before transmitting. The computer can transmit the data if the network is quiet. Otherwise, the computer will back off from the collisions (they will be detected by the protocol) and try to retransmit that data with a random timer.
Address Resolution Protocol (ARP)

ARP is responsible for mapping IPv4 Address# to Media Access Control Address (MAC)#. See Reverse Address Resolution Protocol (RARP) for the reverse mapping. Typically, it is used on broadcast networks such as Ethernet#, Token Ring, and FDDI.

#networking #hardware