Etherchannel - Intro (PAgP, LACP)

There are three different EtherChannel modes: PAgP, LACP, and on.

 

Both in PAgP and LACP mode negotiate to decide active ports.

However, on mode so called static mode no negotiations happen. In other words, unlike dynamic methods, on mode cannot detect connectivity between devices.

 

First, let's look into dynamic link aggregation protocols

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[PAgP]

 

 - Cisco proprietary protocol

 - Advertise messages with multicast (MAC address 0100:0CCC:CCCC)

 - Modes: Auto & Desirable

Mode	Desirable	Auto
Desirable	Yes	Yes
Auto	Yes	No

 - Configure up to 8 ports

 - By default, PAgP ports operate in silent mode, which is optional configuration

   * non-silent is recommended when connecting PAgP-compliant switches together

      => This leads to fast link establishment than if this keyword is not used

 

[LACP]

 

 - Open-standard protocol

 - Advertise messages with multicast (MAC address 0180:C200:0002)

 - Modes: Active & Passive

Mode	Active	Passive
Active	Yes	Yes
Passive	Yes	No

 - Configure up to 16 ports (8 ports: Active, 8 ports: Standby)

 

Second, what about On?

 

[On]

 - Static link aggregation protocols

 - No health intergrity check between links

 

To sum up, PAgP's auto mode and LACP's passive mode has similar mechanism. In these two modes, PAgP or LACP adjancency can be established only after receiving a PAgP or LACP packet.

 

Reference site: https://ipwithease.com/etherchannel-modes-pagp-lacp-and-on/#:~:text=When%20using%20an%20EtherChannel%20mode,in%20EtherChannel%20%E2%80%9Con%E2%80%9D%20mode.&text=Note%20%E2%80%93%20Both%20Switch1%20and%20Switch2,forcefully%20form%20EtherChannel%20without%20negotiation.

EtherChannel Modes - PAGP Mode, LACP Mode & On Mode - IP With Ease

Reference book: CCNP and CCIE Enterprise Core by cisco press