ethernetchannel active + on

fr0xty

Hello,
I was reading the foundation learning guide for ccnp switch, going by what the book explains I understand you should never have one side of the ethernetchannel as on and the other as active. My understanding is ON does not use either LAC or PaGP, will not respond to these packets and the channel will not form. But then I saw the below example:

Switch(config)# interface fastethernet 0/23
Switch(config-if)# channel-group 2 mode active
Switch(config)# interface fastethernet 0/24
Switch(config-if)# channel-group 2 mode active
Switch(config)# interface port-channel 2
Switch(config-if)# switchport mode trunk
Switch(config-if)# switchport trunk native VLAN 99
Switch(config-if)# switchport trunk allowed VLAN 2,3,99
!!!Remote Switch configuration
RSwitch(config)# interface fastethernet 0/23
RSwitch(config-if)# channel-group 5 mode on
RSwitch(config)# interface fastethernet 0/24
RSwitch(config-if)# channel-group 5 mode on
RSwitch(config)# interface port-channel 5
RSwitch(config-if)# switchport mode trunk
RSwitch(config-if)# switchport trunk native VLAN 99
RSwitch(config-if)# switchport trunk allowed VLAN
2,3,99

Is the channel supposed to form? Isn't that config a bad practice?

I appreciate your comments and opinions as I am a bit confused with this example.

Thanks,

Alan -

Dieg0M

LACP will not form but you will create a broadcast storm if the LACP ports are up/up. Loop will form with any combinations of PAgP/LACP and On. Loop can also form if static LAG is configured on one side (ON) and the other side has one of the 2 ports as a root port. I've seen the combination of LACP/On melt around 20 6509 switches in a production environment in less than 10 minutes. Things were so slow we couldn't even log in to those switches and had to isolate the problem by unplugging 1 by 1 uplink ports.

DoubleNNs

Melted them? As in damage them beyond use?

Dieg0M

No physical damage. When I said melt, I mean bring the CPU to 99-100% to the point that they were rendered unusable.

fr0xty

Thanks! that's what I wanted to hear