Ang ethernet technology ang karaniwang technology or standard na ginagamit for LAN (local area network). Ito ang nagde-define ng wiring and signaling for the physical layer of the OSI model(network access layer in TCP/IP).
Ethernet technology is describe as IEEE 802.3 standard.
Gumagamit ito ng Carrier Sense Multiple Access with Collision Detection (CSMA/CD) method at kaya nitong i-support ang speed na up to 100 Gbps.
It can use coaxial, twisted pair and fiber optic cables. Ang ethernet technology din ay gumagamit ng frames (layer 2 information) with source and destination mac-addresses to deliver data.

As you can see in our illustration above, ethernet revolves around many different protocols and standards in our LAN(local area network). Kumbaga, standards are also within standards.
Sa madaling salita mga idol, ang ethernet ay isa lamang “paraan” or standard kung paano nakakapag-communicate ang mga networking devices within local area network. Nagtatakda din ito ng mga standards and “codes” or protocols kung papaano makaka-pag-usap usap ang mga magkaka-ibang networking devices specifically in local area connection.
Pero hindi katulad ng OSI model or TCP/IP model, ang ethernet technology ay bale kabuuan ng isang local area network. Sakop nito ang OSI model pati ang TCP/IP model at iba pang mga protocols.
Ito ang concern kung papaano mag-tratravel ang data from one PC to another device or another PC. Or kung papaano magno-notify ang isang PC na magse-send siya ng data at papaano naman mag-aadvise ang isang PC na magre-receive siya ng data.
For example, before kasi talagang maging advance ang ethernet technology, sa isang network or group of computers noon, hindi pwedeng sabay-sabay mag-send or mag-receive ang mga network devices.
Ang mga computers ay connected lamang sa isang “line of connection” usually called “single shared physical bus” then may limit ang haba ng wire(before it was coaxial cable).
Bago makapag-send ng data ang isang device, mag-aadvise muna siya or mag-checheck kung walang ibang device ang nag-papadala ng data or information. Ganun din sa pag-receive.
Think of it like crossroad, bago ka tumawid, you have to check and look left or right kung merong sasakyan. Ngayon, with the help of Ethernet technology, let say sabihin natin na meron tayong “overpass” para pwede ka nang tumawid kahit may dumadaan man na sasakyan or wala(just for the sake of explanation).
Or para mas madali natin maintindihan, dahil nga sa CSMA/CD na ginagamit ng ethernet technology, naiiwasan ang collision at nagiging smooth ang network communication.
Pero since advance at marami ng natuklasan technology ngayon, it can happen na pwede ng mag-send at mag-receive ng data ang isang device simultaneously. Idi-discuss natin ang mga ito sa susunod.
Kagaya nga ng nabanggit natin sa taas, meron itong collision detection para maiwasan ang collision or “pagru-rumble” ng mga frames. Na-oorganize ang pag-send at pag-receive ng information or data sa pamamagitan ng ethernet technology using CSMA/CD.
Duplex and Half-duplex
This is very basic. But I can assure you na kailangan din natin itong daanan para mas madali natin maintindihan how network works and how it evolves through the years.
Kapag sinabi nating half-duplex, it’s only a one-way of communication. It cannot send and receive at the same time. Kung send, sending lang. Kung receive, receiving lang. Pero hindi sabay. Ibig sabihin, no simultaneous communication can happen.

Take for example, a walkie-talkie. A traditional walkie-talkie operates in half-duplex mode. Hindi pwedeng mag-receive and mag-send ng “signal”. It’s either you talk or listen. Kung nakasakay ka na ng mga fx, you probably heard and see how these drivers used walkie-talkie.
Ginagamit nila ito para makapag-communicate sila about traffic at maka-iwas sa mga nanghuhuli. Right?
If you ever observed, hindi sila pwedeng mag-salita ng kausap niya. It’s always the first one talk and the other listen. Kapag tapos nang mag-salita yung isa, that’s the time na pwede na sumagot yung kausap niya. Kaya lagi silang meron confirmation, “do you copy? over”.
That’s how half-duplex operates in a sense.

In networking, hub is a good example of device that operates in half-duplex. It cannot send and receive at the same time. So ibig sabhin, the port is either on the sending mode OR in receiving mode.
Now pagdating sa full-duplex, it a two-way communication na. Ibig sabihin, it can send AND receive at the same time. In networks, a modern switch, like a Cisco switch also operates in full-duplex mode.

Ibig sabihin, the device connected to its port can send and receive “signals” at the same time. That’s why nung una, a switch is also called “an intelligent hub”.
Now, from experience, sa troubleshooting, minsan a device can have issues connected to a switch port. You may need to check the interface setting or configuration. Minsan naka-half-duplex at yun ang nagiging problema(lalo na kapag may mga ibang devices na naka-connect doon before).
Some of the commands na pwede mong magamit are the following:
- show run interface [interface number]
- show interface [interface number]
We need to remember this kasi minsan kailangan natin ito sa troubleshooting or di kaya naman sa interview.
Got this?
By now, you now understand what is half-duplex and full-duplex is.
Collision and broadcast
Let’s also talk about collision and broadcast to give us more in-depth fundamentals kung paano nagsimula ang network.
Collision domain is where a group of devices where a frame or signal can collide to each other. Now, nabanggit natin kanina, yung mga sinaunang hub is operating in a half-duplex mode right? They are also in a one “big collision domain”. Ibig sabihin, they cannot send and receive signals at the same time.

As you can see in our simple illustration above, we have a computer sending a signal on the left. Ibig sabihin, it can only send but cannot receive signal at the same time. You can also see na meron tayong mga computers on the right, although they will “try to send” a signal din, since may nag-sesend na nga, hindi ito mangyayari.
A collision happens when one or more device try to send signals at the same time. Ibig sabihin, mag-cocollide yung signals nila. Mag-babanggaan kumbaga.
That is basically what we have in an old ethernet setup lalo na nung ginagamit pa natin ang mga sina-unang hubs.
Hub is consider a big collision domain. Ibig sabihin, pwedeng mag-collide or mag-banggaan ang mga signals. Kahit pa gaanong kadaming ports or gaano kadaming devices ang naka-connect dito, it is a one big collision domain.

As you can see in our illustration above, we have two different scenario kung saan sa una, isang computer lang ang naka-connect sa ating hub. It’s a collision domain. Pero in the second one, we have multiple computers, it is still one collision domain. Kahit pa mag-dagdag tayo ng another hub, it will be consider as one big collision domain.

Does it make sense now?
Since ang hub ay isang malaking collision domain, all devices connected to it can have a collision. If you can recall, ang ginagawa lang naman ni hub ay ire-send or ire-generate yung signal na natanggap niya sa lahat ng ports “without” analying or examining(kasi wala siyang ganung capability). Unlike the switch which can analyze traffic and make a filtering decision. Pero dito pumapasok ang tinatawag natin na broadcast.
Ang broadcast domain is where group of devices can receive a broadcast. Ito yung mga devices na pwedeng-mag-communicate sa isa’t isa under layer 2 ng ating OSI model through broadcast.
If you can recall, the function of a switch is to send a broadcast to all of the devices connected to its ports(sa unang beses silang nag-communicate).
Right?
All those devices are part of a broadcast domain. Kasi ang switch ay isang malaking broadcast domain.

When switch receives a “frame”, di ba ise-send niya sa lahat ng kanyan ports(maliban sa source port) yung frame as a broadcast. This is because it needs to know kung saan port naka-connect yung destination device. Those are part of a broadcast domain.
Switch stop or minimize collision(dahil it operates in full-duplex mode). Ang isang port ng switch is consider a collision domain. But the whole switch and all devices connected to it are part of a one big broadcast domain.

I hope by this far, you now have the understanding between the difference of collision and broadcast.
Maganda na maintindihan natin ito to “solidify” our knowledge. Kasama ito sa mga fundamentals an magpapatibay ng ating pundasyon when it comes to networking.
idol salamat dito sa lecture.
Welcome idol! 🙂
sir, THANK YOU! aminado ako na hindi ako nakinig sa prof ko sa networking subject kase akala ko mas mag fo-focus nalang ako sa sys dev, since yun naman ang pinaka course ko. but ngayong nag oojt na ko, saktong sa networking po ako na assign. so nag isisisi ako na hindi ako nakinig sa prof ko. so review to the max ako. thank you po sa blog nyo. (*le cries*)
Welcome Noire. Glad to help. God bless!
Thanks idol for creating this “very informative” blog for all aspiring CCNAers like me.
Question ko lang idol…. Bakit sa serial cable one end is dce and the other is dte whereas both ends naman ng connection can be connected with any of those devices? (ie…2 routers connected using a serial cable.) both devices are dce but the other is connected to dte side.
Thanks idol……
Hi Sir Billy! Ask ko lang po kung considered as DCE po ba ang mga cable? Thanks po and God bless! 🙂
I think yes Sam. Check ko to confirm. 🙂
Sir ano po ba ang Router DCE or DTE? Kasi may question sa exam tungkol sa ethernet technologies, at may sagot na “A Router is commonly considered as a DTE Device”? TIA sir Have a good day everyday.
Hi idol! nagustuhan ko po itong topic kaso medyo naguluhan ako kung ano ibig sabihin ng DTE at DCE. Suggest ko lang po na padagdag ng details. Salamat! And, gusto ko rin po malaman kung paano nagwowork itong DTE and DCE sa Router to Router
Bangis mo idol salamat ng marami.
Thanks Mark!
Hi Billy. Thanks for this wonderful site to help fellow Filipinos learn more about CCNA in a very relatable way. Ask ko lang kase nalito ako dun sa sinabi mo na Ethernet defines wiring and signaling in the physical layer of the OSI model pero later on sinabi mo rin na Ethernet is different to OSI and TCP/IP kasi ang ethernet ay kabuuan ng interconnection sa isang LAN and thus sakop ng ethernet ang OSI and TCP/IP. Yung ethernet po ba ay for physical layer lang or sakop nya rin lahat ng layers ng OSI? Thanks.
Ethernet covers layer 1 and layer 2.
OSI covers “standard” or ways kung papaano magcocomunicate ang mga devices. Thanks!
Very useful blog..thanks idol
Nagi-start po ako ngayon sa self study ko for CCNA, at dito na nga po ako ngayon sa Ethernet, salamat po at tagalog po ang lecture nyo, kasi talagang ang hirap intindihin pag-english, kaya naman mula network to TCP/IP model ay naunawaan ko, pero bigla po ako naguluhan, ang Ethernet po ba ay parang RJ45? or ung kinakabitan ng RJ45? at iyon po bang OSI and TCP/IP model is ways papaano ang flows ng communication ng devices? at pra mangyari ang OSI and TCP/IP model ay dapat merong Ethernet (kasi nasa isip ko po na Ethernet is kind of wiring like RJ45)?
LAN ay para ba tong chart kung pano magdudugtong dugtong ung mga devices?
sorry po kung ganito tanong ko, gusto ko lng malinawan tlg kung nakikita ba ng mata or I mean accessories or devices ba itong mga Ethernet, TCP/IP model, OSI, LAN etc. or just like a chart.
salamat and God bless you more 🙂
salamat talaga Idol the best to na lesson ngayun self study nalng ako kasi ang laki ng tulong ng blog mo, salamat talaga po
it help us a lot, im doing self study using this billy’s blog bago ako mg enroll, thanks for being unselfish for sharing your knowledge. hi five ! ! !
grabeh lupit napakabait hero ka sir konti lang nagtyatyaga magturo ng ganito in tagalog pa… pagpatuloy nyo po madami kayo natuturuan pramiss
Ngayon ko nalaman kahalagahan ng course na tinapos ko ???? maraming salamat mga ka-nets!
Maraming Salamat Idol Billy,
Thank you sa blog mo. Ito ang dapat basahin lalo na sa panahon ngayon ng Lockdown.
God bless you. Pa accept naman sa FB Lodi =)