LACP –
LACP abbreviation in networking stands for Link Aggregation Control Protocol which is widely used in a switching infrastructure.
LACP is an open standards-based protocol for link aggregation alternative to PAGP (Cisco Proprietary).
LACP packets flow over the ether channel capable ports. It assigns roles to EtherChannel endpoints.
There are two parameters that define the role of os endpoint and which ports will be active in an Etherchannel:
Lowest System Priority is preferred
If no changes are made to the priority value then the switch with the lowest MAC address will become decision-maker as to what ports actively participate in EtherChannel at a given time.
Lowest Port Priority is preferred
In LACP we may bundle as much as 16 ports together and only maximum of 8 are active at any given point in time and rest are on standby just in case if any active port fails.
Related – PAGP VS LACP
If no changes are made to the port priority value then first 8 ports (Assuming bundle is of 16 ports) are chosen as active ports in the bundle based on their low port number.
LACP MODES OF OPERATION :
Active Mode: In this, the switch actively asks the far end to negotiate an ether channel.
Passive Mode: In this mode, the switch waits to hear from the far end to negotiate an ether channel and doesn’t actively ask to negotiate an ether channel.
Now let us take an example as below to understand the configuration of LACP based ether-channel between two switches :
Switch 1 has MAC of “aa.aa.aa.aa.aa.aa” and switch 2 has MAC of “bb.bb.bb.bb.bb.bb”
Switch 1 forms ether-channel with switch 2 using LACP and switch 1 will have system priority of 100 to make it the decision-maker.
Ports Gi 2/1 – Gi 2/4 & Gi 3/1 – Gi3/4 become the active ports as we configure the port priority of 100 on the ether channel and ports Gi 2/5 – Gi 2/8 & Gi 3/5 – Gi3/8 from will become the standby ports as they will have default port priority value of 32768.
CONFIGURATION
switch1(config)#channel protocol lacp
switch1(config)# channel-group 1 mode active
switch1(config)# lacp port priority 100
switch1(config)#exit
switch1(config)# interface range Gi2/5 – 8 , Gi3/5 – 8
switch1(config)#channel protocol lacp
switch1(config)#channel-group 1 mode active
ABOUT THE AUTHOR
I am here to share my knowledge and experience in the field of networking with the goal being – “The more you share, the more you learn.”
I am a biotechnologist by qualification and a Network Enthusiast by interest. I developed interest in networking being in the company of a passionate Network Professional, my husband.
I am a strong believer of the fact that “learning is a constant process of discovering yourself.”
– Rashmi Bhardwaj (Author/Editor)
