Configuring a Layer 3 Etherchannel

[MikeNY85]

Hello Network professionals, please help with this weird question..

If you are configuring a Layer 3 port-channel interface with LACP. The configuration on the first device is complete, and it is verified that both interfaces have registered the neighbor device in the CDP table. Which task on the neighbor device enables the new port channel to come up without negotiating the channel?

interface g2/0/0
channel-group 1 mode active
interface g4/0/0
channel-group 1 mode active
interface Port-channel1
ip address 203.0.113.65 255.255.255.252

%LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to down

A. Configure the IP address of the neighboring device.
B. Bring up the neighboring interfaces using the no shutdown command.
C. Change the EtherChannel mode on the neighboring interfaces to auto.
D. Modify the static EtherChannel configuration of the device to passive mode.

The command "no switchport is missing", but that's the question as is. I am assuming it's B since none of the other options make sense.  I would appreciate if any of the professionals confirms that. Thank you and much appreciated!

[Enes Simnica · Accepted solution]

hello G. In my opinion the correct answer is D, because this scenario involves LACP configuration where we want the port-channel to come up without negotiation. When using LACP, setting one side to passive mode allows the port-channel to form without the normal negotiation process, as long as the other side is active. Since the question specifies bringing up the port-channel without negotiation and we know LACP is being used (as its a Layer 3 port-channel/), modifying the configuration to passive mode on the neighbor device is the proper solution. The other options don't address this specific requirement. so  IP configuration is irrelevant, interfaces are already up (per CDP), and auto mode is for PAgP, not LACP. The key is understanding that passive LACP mode enables the port-channel to form without the typical negotiation that would occur if both sides were active.

hope it helps G...

-Enes

[MikeNY85]

Thanks for clarifying, much appreciated!