Encapsulation Types

[nnn_sss22]

Hello

What is function of encapsulation and please explain the encapsulation protocols. dot1q , isl, negotiation. thanks

Regards

[Leo Laohoo]

Inter-Switch Link and IEEE 802.1Q Frame Format

[Julio E. Moisa]

Hi

The encapsulation is useful to define the format / trunking protocol to be used under a trunk interface, for example the current standard format to be used over a trunk interface for most of the manufacturers is  IEEE 802.1q. It is used to interconnect switches and routers which is the case of router in a stick scheme.

ISL is Cisco proprietary, it was created to interconnect the Cisco switches only, It cannot be used on third party switches

Negotiate: it will auto negotiate the parameters for the ports, by default it is enabled.

Also I recommend this link:

http://www.omnisecu.com/cisco-certified-network-associate-ccna/what-is-dtp-dynamic-trunking-protocol.php

Hope it is useful

:-)

[Leo Laohoo]

Julio, 

Careful with your responses.  This thread was created to answer a school assignment.  :)

[Julio E. Moisa]

ohh ok, thank you Leo.

:-)

[nnn_sss22]

Hello,

Now ISL and negotiate are eliminated in new version of IOS. right?

[Julio E. Moisa]

Yes, the new switch models like 3850 have implicity the dot1q protocol. I have not found any way to enable ISL

[nnn_sss22]

In old switches by default negotiation is on. its means DTP is enable? negotiation is third type of Encapsulation protocol which by default is on?

In new switch this type of encapsulation is eliminate. now still DTP is enable by default? if yes then DTP will use it by default 802.1q encapsulation protocol?

[Leo Laohoo]

the new switch models like 3850 have implicity the dot1q protocol. I have not found any way to enable ISL

3650/3850 don't support ISL any more.  Future Cisco switches will not be supporting ISL. 

[Julio E. Moisa]

Thanks, Yes you are right.

[nnn_sss22]

In old switches by default negotiation is on. its means DTP is enable? negotiation is third type of Encapsulation protocol which by default is on?

In new switch this type of encapsulation is eliminate. now still DTP is enable by default? if yes then DTP will use it by default 802.1q encapsulation protocol?

[Leo Laohoo]

In new switch this type of encapsulation is eliminate.

Before I make any response to this school work, can you explain what is DTP and what it is used for? 

[nnn_sss22]

When two switches create a trunk link then both switches need to trunk negotiation. for example which encapsulation protocol will be use between of them for negotiation.

That ports which through both switches are connected if the ports are dynamic desirable on both side or one side is dynamic desirable and other side is trunk then DTP will use for encapsulation protocol. right?

[Leo Laohoo]

When two switches create a trunk link then both switches need to trunk negotiation.

Define "create".  Is the trunk port created manually (human intervention) or automatically? 

For example, I have two modern switches.  I configure VLAN interfaces only and then I connect the two switches together.  When does DTP step in?

[nnn_sss22]

Define "create".  Is the trunk port created manually (human intervention) or automatically?

When we make switchport mode trunk manually then both switches need to trunk negotiation. 

The ports that both switches are connected through are either set to "dynamic desirable" on both sides, OR with one side dynamic desirable and other side  trunk. The DTP will then run and it will use encapsulation protocol.

By default in old switches DTP is enabled and use "Negotiate" encapsulation protocol.

There are 3 encapsulation protocols. 1) dot1q 2) ISL 3) Negotiate

The new IOS version eliminates negotiation protocols "ISL" and "Negotiate" Only one protocol is used: dot1q.

If we set switchport mode trunk manually, dot1q encapsulation will run automatically.

If DTP is running on trunk link then also dot1q encapsulation will run automatically.