SWITCH - Dot1Q is IEEE 802.1Q, the standard for trunking encapsulation. On Cisco switch dot1q on trunk ports which permit labeled outlines to be transported on a trunk connect, permitting numerous VLANs to navigate through one interface. This expands the VLANs over the network.

When designing trunk ports, both closes of the connect must have the same local VLAN. In case the local VLAN does not coordinate, an mistake message will be shown on the support.

below are trunking modes:

- dynamic auto - Interface is able to change over to a trunk connect on the off chance that the other conclusion of the interface is set to trunk or alluring mode. Usually the default switchport mode.

- dynamic desirable - Interface effectively tries to change over to a trunk connect. The connect gets to be a trunk in case the other conclusion is set to trunk, alluring, or auto mode.

- trunk - For all time places the interface in trunk mode. Interface gets to be a trunk indeed in the event that the other conclusion isn't a trunk interface.

When an interface is in trunk mode, it is able to send and get activity from all VLANs. It is conceivable to permit as it were particular VLANs to navigate over the trunk.

Load Sharing

Needs can be set on a parallel trunk harbour so that the harbour carries all activity for a given VLAN. A trunk harbour with the higher need (lower esteem) for a VLAN is sending activity for that VLAN. The trunk harbour with the lower need (higher esteem) for that same VLAN is within the blocking state for that VLAN.

Trunk Settings

Trunk ports can be arranged into an EtherChannel harbour bunch with all trunk interfacing with the same arrangement. Any changes to the harbour bunch will engender the alter to all ports portion of the bunch.

Configuring VLAN Trunks

To impair trunking all together, constrain the switchport into get to mode.

switchport mode access

On a few switches you must indicate switch dot1q (802.1q) as the epitome utilizing the command:

switchport trunk encapsulation dot1q

Interface ports into both switches and for each interface issue the commands:

config t

interface interface-id

switchport access vlan vlan-id !This sets the VLAN which the harbour will utilize when it is now not in trunking switchport mode {dynamic {auto | desirable} | trunk}

switchport trunk encapsulate dot1q

switchport trunk native vlan vlan-id

end

Verify the trunk configuration and operation for each interface:

show interfaces interface-id switchport

show interfaces interface-id trunk

 
https://mobileinfoworld.com/switch-dot1q/

Bundling multiple ports into one logical interface is a common configuration. It is otherwise known as bundling, port channel or EtherChannel. You can combine multiple interfaces into one of these three modes:

- LACP

- PAgP

- On

LACP

Link Aggregation Control Protocol is the standard 802.3ad. You combine multiple links into a single logical link to increase bandwidth and redundancy. All links participating in a single logical link must have the same settings such as duplex mode, link speed, and interface mode such as access or trunk. You can have up to 16 ports in an LACP EtherChannel but only eight can be active at one time.

LACP can be configured in either passive or active mode. In active mode, the port actively tries to bring up LACP. In passive mode, it does not initiate the negotiation of LACP.

There are a few parameters which can be configured with LACP ports:

- System Priority - Forms the system ID and is used during negotiation.

- Port Priority - Used to decide which ports should be put in standby mode when there is a limitation or something preventing a port from aggregating.

- Administrative Key - Defines the ability of a port to aggregate with other ports.

In the event one of the links within an LACP bundle fails, traffic continues to flow on the other available links in the bundle.

PAgP

Cisco's proprietary alternative to LACP, Port Aggregation Protocol. It also creates Etherchannel links and is configured similarly to LACP. Configuring PAgP properly and it will automatically configure individual ports into a single logical link.

There are two modes for PAgP:

- auto - This is the passive negotiating state which responds to PAgP packets.

- desirable - Places interface into an active negotiating state.

Having two ends of a PAgP link in auto mode will not result in a PAgP link because neither will negotiate to bring up the PAgP EtherChannel. PAgP protocol data units (PDUs) are sent and received on the lowest numbered VLAN of the trunk link.

You can have up to eight ports in a single PAgP EtherChannel. Just like LACP, all ports in a PAgP EtherChannel must have the same speed and duplex settings.

EtherChannel Manual

Switchports can be configured to bypass LACP or PAgP by simply changing the mode to on. This mode is used to manually configure EtherChannel. This mode can be used if the device on the other end doesn't support PAgP or LACP.
https://mobileinfoworld.com/configuring-lacp-pagp-manual/