Let’s talk about DTP on this lesson.
Ang DTP or dynamic trunking protocol which is concerned in negotiating “trunking” on a link between two vlan-aware switches. It’s a Cisco proprietary protocol. Meaning, created by Cisco for Cisco devices only.
Kasi di ba, in an enterprise, hindi lan naman isang switch ang ginagamit natin for our network. We need to have multiple switches to provide connection sa ating mga end devices. Now, of course, yung mga switches natin na yun are also connected to other switches. Either their uplink or other access switches in the network.
Kapag ang switch ay kailangan natin i-connect sa another switch, we need to have the ports or interface set as “trunk” kung saan sila connected. Ibig sabihin, kelangan naka-trunking sila. This is where dynamic trunking protocol comes in.
As you can see in our simple illustration above, we have two switches and they are connected together. Connected sila in their fastethernet 0/1(fa0/1) port pareho. Ibig sabihin, those ports need to be in trunking mode para makapag-communicate at makapag-pasahan sila ng information especially there are different vlans between them.
Gets mo idol?
If we look back, doon sa Cisco hierarchical model, we have access switches connected to core or distribution switches natin. Yung mga ports or interfaces kung saan sila connected ay kailangan naka-set as “trunk” para magkita at magka-usap sila.
It should look like this.
Those ports na connecting to other switches should be in trunk para nga magka-usap usap sila at makapag-pasahan ng mga switch-related information and updates.
Make sense idol?
Kapag pinag-usapan natin ang DTP or dynamic trunking protocol, meron tayong 2 types of encapsulation.
- 802.1Q – ang 802.1q ay industry standard trunking encapsulation na karaniwang ginagamit sa mga switches. Ibig sabihin, it can work with Cisco or other vendor. Sa 802.1Q trunking encapsulation, dtp packets or frames are setn via native vlan.
- ISL – ang ISL or Inter-Switch Link ay Cisco proprietary trunking protocol. Meaning, gagana lang para sa mga Cisco devices. With ISL, dtp packets are sent via VLAN 1.
Those are the two types of trunking encapsulation na ginagamit natin sa mga trunk ports. Pero as of today, 802.1Q na ang karaniwang ginagamit. In fact, ISL has been depreciated already by Cisco.
How do we apply this?
Gamit yung simple diagram natin kanina, let’s have an example.
As you can see in our sample configuration, if I’m going to configure Switch A to connect to Switch B via fa0/1, kailangan naka-set ito as trunk. Kagaya ng ginawa natin. And then we need to specify kung anong “trunking encapsulation” ang gagamitin nila. We set “dot1q” meaning it will use 802.1Q encapsulation.
Now, since we called this “dynamic trunking protocol”, it is possible na ang mga ports can formed or become a trunk kahit hindi natin ito i-set(depending on the mode of the interface or port).
What do I mean?
Let’s talk about the different modes of an interface or ports ng mga switches kung kailan sila pwedeng maka-formed ng trunking.
Different switch port modes
- Access – set port to non-trunking mode permanently even if the other side agree or not. Ibig sabihin, if the port or interface ng ating switch ay naka-set as “access port”, hindi tayo makakabuo ng trunk or trunking.
Take note ha, “kahit isang port” lang ang naka-set na access sa kahit alin mang switches natin, hindi ito makaka-buo ng trunking. Access port are used mostly in end devices like pc.
This is how we set the port or interface as an access port.
- Trunk – it sets port to “trunk” permanently. On this one, it will form a trunk kapag si-net natin ang naturang port as trunk mode given na ang kabilang side ay naka-set as trunk, dynamic auto or dynamic desirable.
This is how we set the port or interface as trunk port(or dynamic auto or dynamic desirable).
- Dynamic auto – mostly set as default interface mode in Cisco switches. Makaka-form tayo ng trunking sa naka-set na dynamic auto na port kung ang katapat na port nito ay trunk or dynamic desirable.
Notice na kapag parehong naka-auto or dynamic auto ang mode ng ports or interface ng dalawang switches, hindi ito magfo-form ng trunk.
Kumbaga, magkakahiyaan sila. Since naka-set ito as auto, inaantay lang ng port or interface kung anong naka-set sa kabilang port. Again to form a trunk, dapat naka-trunk or dynamic desirable lang.
Configuration is the same lang naman with the above(choose dynamic auto).
- Dynamic desirable – In dynamic desirable, it’s actively looking to form a trunk. Ibig sabihi, makaka-form tayo ng trunk kapag ang naka-set na mode sa port or interface ay trunk, dynamic auto or dynamic desirable. Meaning, kahit alin sa mga yan magfo-form ito ng trunk(except of course sa access mode). It looks like this.
Pareho lang din ng configuration, kelangan lang natin piliin yung dynamic desirable.
- No-negotiate – in this mode, no trunking will be form kahit ano pa ang mode ng kabilang interface. Kumbaga, this will disable DTP.
In summary, it will look like this.
These are the fundamental topics na kailangan natin malaman in terms of dynamic trunking protocol. We will do the configuration of them sa ccna masterclass na.
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Let’s move on to another lesson.