On this lesson, we’re going to discuss the CDP and LLDP topic. Kasama ito sa exam at sure ako na malaki rin ang maitutulong nito sa inyo pagdating sa real world. Maiksi lang topic na ito so umpisahan na natin!
What is CDP?
CDP stands for cisco discovery protocol. Ito ay ang protocol na ginagamit ng mga Cisco devices para makita or ma-discover ang mga information ng ibang Cisco devices na directly connected sa kanila. Ibig sabihin, I can only see other device information kung directly connected or naka-connect talaga sila sa isang Cisco device.

This can be very helpful sa mga troubleshooting lalo na’t walang network diagram or hindi ka pa masyadong pamilyar sa environment.
Through CDP, pwede mong makita or i-check kung anong Cisco device ang connected sa isang Cisco device kasama ang kanilang mga information.
Ito ang ilan sa mga information na pwede mong makita from a connected device using CDP commands:
- Cisco IOS XE version running on a Cisco device
- Duplex setting
- Hardware platform of the device
- Hostname
- IP addresses of the interfaces on devices
- Interfaces active on a Cisco device, including encapsulation type
- Locally connected devices advertising Cisco Discovery Protocol
- Native VLAN
- VTP domain
Again ang CDP ay Cisco proprietary or gumagana lamang sa mga Cisco devices. For other devices, LLDP naman ang ginagamit. We’ll talk about that later.
Ito naman ang mga karaniwang CDP commands na ginagamit sa exam and sa real world.

- This will enable cdp in case ito ay disabled, pero by default enabled na ito sa mga Cisco devices.

- Ito naman ang command to disable the CDP on the device

- Ginagamit ang command sa taas kung gusto nating ma-disable ang CDP for certain or specific interfaces lamang.

- This will show the summary of directly connected Cisco devices sa ating device

- Dito naman natin makikita ang complete details ng bawat device na connected sa device kung saan tayo naka-login. Information like hostname, IOS version, IP address, platform at iba pa gaya ng sinabi ko sa taas.
Let me show you in action.

As you can see, meron akong simpleng topology sa taas. We have R1 and R2 connected on each other. From R1(gi0/0 with ip 192.168.1.5) connected siya kay R2 sa (gi0/1 na interface with ip 192.168.1.5).
Let’s use CDP to get information from each of the device.

Gaya ng nabanggit ko sa taas, using show cdp neighbors, nakikita ko ang basic information about R2. Model, anong interface connected etc. Take note ha, I’m on R1.
Let’s try another one.

As you can see mga idol, using the show cdp neighbors detail command, I was able to pull up all related information sa aking neighboring device(which is R2). Information like IP address, IOS version, platform, VTP, duplex etc. In short, mas detailed.
Again, this comes very handy in the exam kasi may mga tanong na kelangan mong hanapin yung sagot pero wala sa mismong device kaya kelangan mong mag-CDP or meron din times na hindi mo alam kung pano mo i-aaccess yung other device. With CDP, you can use all these information in any way na kelangan mo.
In real world mga idol ganun din. Sabi ko nga kung walang network diagram or hindi ka masyadong pamilyar sa environment, si CDP and magiging mata at gabay mo para makita kung anong mga Cisco devices ang magkaka-connect.
Of course, given na naka-enable ang CDP sa mga devices.
Let’s move on to LLDP.
What is LLDP?
LLDP means Link Layer Discovery Protocol. Ito ay isang open-standard protocol na ginagamit for discovery ng connected device.
Since si CDP ay proprietary at pang-Cisco devices lang, we have LLDP para naman sa mga other vendors or non-Cisco devices. The function is the same, ito ay para makita at makuha natin ang mga information ng directly connected devices sa device kung saan tayo naka-login. Here are the information na pwede natin makita using LLDP command or protocol:
- System name and description
- Port name and description
- VLAN name
- IP management address
- System capabilities (switching, routing, etc.)
- MAC/PHY information
- MDI power
- Link aggregation
Since it’s an open-source protocol, it can also work in Cisco devices. Pero kadalasan, we use CDP in Cisco in real world.
In order to enable lldp in a Cisco device, we just need to enable the lldp command. Take note, lldp is not enabled by default in Cisco devices kasi nga meron itong proprietary na CCDP protocol.

As you can see, lldp is not enabled by default in a Cisco router. In order to enable it, we just use the command “lldp run”.

Let’s use the same topology that we have earlier to pull-up some information gamit ang lldp.


As you can see, we also got the same information like what we have in using cdp earlier right?
Take note ha, I’m on R1 ulit and using lldp to pull-up this information from R2. Let’s pull-up more detailed information from R2.

See?
Now we have more detailed information from R2 kahit na kay R1 tayo using the lldp command. Imagine how this becomes helpful when you’re dealing with hundreds of devices tapos wala kang diagram?
Napaka-helpful di ba?
And again, it will only work if lldp is enabled on the device.
We will not go into details about LLDP. Always remember na it works the same way as CDP. CDP is proprietary for Cisco devices. LLDP is an open-source.
Note: CDP and LLDP operates in layer 2. This might be included on the exam.
We’re good now?
Let’s move on to another lesson.
Hi Sir Billy,
Sir, I am very interested on what you discussed here, lalo sa laman ng ebook, I want to learn about Network and security included po ba sya sa ebook? sa office po kase wala naman po kaming cisco, just a simple small time business lang po ang pinapasukan ko but I want to learn more deeper about being IT.
Hoping sir on your quick answer
Thank you in advance…
God Blessed
Hi Mervin, thanks for the comment. All details about the ebook can be found here. THanks!
Great Article… I love to read your articles because your writing style is too good, its is very very helpful for all of us and I never get bored while reading your article because, they are becomes a more and more interesting from the starting lines until the end.
Idol Billy, ACL po next pls
ACL is included in the ccna basic and fundamentals ebook.
Hi,
Sir Billy, meron po ba kayong ibang blog na patungkol parin po sa IT. For example po blog na pweding mag help sa pag self study about sa servers po. Gusto ko rin po kasi malaman pano yun. Or kung meron po ba kayong blog na ma’eerecommend. Nakakainspire po yung story kung saan ka dinala ng hunger for knowledge about IT. Ganun po rin kasi ako ngayon, gusto ko po talaga matoto.
Eto lang about sa IT idol, ccna career. Salamat
Hi idol Billy!
Just passed my CCNA R&S this May 30, 2018. Gusto ko po sana aralin ang course na CCNA Security, May maipapayo po ba kayong websites, or any study materials na pwede gamitin ko sa pagaaral ng CCNA Security ng libre? Maraming salamat Idol