LACP Hot Standby
July 22, 2012 3 Comments
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.
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?
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
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.