LACP Hot Standby


LACP allows for up to 16 ports to be configure to be part of a port channel but only 8 are active at any point in time and the others are in a hot standby state.

When one port fails the switch will choose a replacement from the hot standby pool. Priorities can be assigned such that some ports will be chosen to be a part of the port channel ahead of others.

LACP chooses port based on the following

  • LACP system priority
  • System ID (the switch MAC address)
  • LACP port priority
  • Port number

Note: with LACP numerically LOWER values have a HIGHER priority

Configuring LACP priorities

Configure System ID (default is 32768)

Switch(config)#lacp system-priority 1000
Switch(config)#
Switch(config)#do sh lacp sys-id
1000, 0014.1c66.0800

Configure LACP Port Priority (default is 32768)

Switch(config)#int g1/0/19

Switch(config-if)#lacp port-priority 100

This would make this port more desirable than the other ports.

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About ccie4all
Hello, and welcome to the first post of my CCIE blog This blog has got one simple goal and that is to improve our skills in Cisco Networking field so we can become best engineers on a job market. Wordpress Blog https://ccie4all.wordpress.com/ information about the changes made to Gns3 BGP , MPLS and R&S CCIE labs. In order to access and download all provided materials and receive important updates from Gns3 BGP , MPLS and R&S CCIE labs under GNS3 tab in the main header please go ahead and subscribe to https://ccie4all.wordpress.com/ ! All other posts have not been affected and can be accessed at any given time. Enjoy ! Tom

3 Responses to LACP Hot Standby

  1. dmsandyc says:

    Tom, do you know if it’s possible to configure LACP in a 1+1 scenario? What I mean is 1 active and 1 standby port?

    • ccie4all says:

      hi dmsandyc

      not entirely certain what you mean by 1 active and 1 standby port ? do you mean 2 switches connected with an etherchannel (minimum 2 ports bundled) where one of the ports in both port channels is in standby mode ?

      have not had a chance to test this one out yet however after you configure an EtherChannel, the configuration that you apply to the port-channel interface affects the EtherChannel; the configuration that you apply to the LAN ports affects only the LAN port to which you apply the configuration. To change the parameters of all ports in an EtherChannel, apply the configuration commands to the port-channel interface

      Basically you can play with an individual ports within an ether channel and assign different priorities them
      Router(config-if)# lacp port-priority “priority_value”

      ill post it as soon as ive figure it out

      • dmsandyc says:

        Hi Tom, thanks for the reply, it’s probably an unusual configuration for LACP and there may be a completely different and more suitable way of doing it, but basically I have two servers, one active, one standby. I was thinking I could connect both servers to a switch and have those switch ports in a small group with only the first port active and the second port ready to be made active if the first goes down. It’s not what the technology was designed for, but it might work.

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