2.4 Configure and verify (Layer 2/Layer 3) EtherChannel (LACP).
Objective 2.4 sits in Network Access, which carries 20% of the CCNA exam. The questions below are original, written from the official objective title above, and each explanation cites the Cisco page it rests on.
Objective title verbatim from the official objectives. Cisco exam page ↗
A worked example
Shown solved, with the whole explanation open: this is what every question here carries.
Both switches carry the same uplink configuration and the bundle never comes up.
SW1# show etherchannel summary
Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
U - in use f - failed to allocate aggregator
Number of channel-groups in use: 1
Number of aggregators: 1
Group Port-channel Protocol Ports
------+-------------+-----------+-------------------------------------
1 Po1(SD) LACP Gi1/0/1(I) Gi1/0/2(I)
SW1# show running-config interface gigabitethernet1/0/1
interface GigabitEthernet1/0/1
switchport mode trunk
channel-group 1 mode passiveWhat is stopping the bundle?
The concept
Aggregation negotiation has an initiating role and a responding role. A responder answers control frames it is sent and never sends the first one, so two responders facing each other exchange nothing and each port stays an ordinary link.
Why this answer
The summary marks both members stand-alone and the channel down, and the interface carries the responding keyword on a peer configured the same way. Switching one side to active gives the pair an initiator, and both members then move to bundled.
- APort priority selects which members bundle when there are more candidates than slots. It is not a condition of forming the channel.
- BControl frames ride the lowest numbered VLAN on a trunk and are unaffected by trunking. Trunk members bundle routinely.
- CA channel group command creates the logical interface on its own for Layer 2 ports, and the summary already lists Po1.
- Correct. Two responders leave nobody to send the first control frame.
Now you: objective 2.4 questions
No account needed. The explanation opens when you answer.
Sample question 1 of 2
Two trunk ports assigned to channel group 2 stay stand-alone, and both sides are set to the initiating LACP mode.
SW1# show etherchannel summary
Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
R - Layer3 S - Layer2
U - in use
Group Port-channel Protocol Ports
------+-------------+-----------+-------------------------------------
2 Po2(SD) LACP Gi1/0/3(I) Gi1/0/4(I)
SW1# show running-config interface gigabitethernet1/0/3
interface GigabitEthernet1/0/3
switchport mode trunk
switchport trunk allowed vlan 1,10,20
channel-group 2 mode active
SW1# show running-config interface gigabitethernet1/0/4
interface GigabitEthernet1/0/4
switchport mode trunk
switchport trunk allowed vlan 1,10,20,30
channel-group 2 mode activeWhat keeps them apart?
Sample question 2 of 2
A routed EtherChannel between two switches passes no traffic, and the neighbor cannot ping across it.
SW1# show running-config interface port-channel 5
interface Port-channel5
no switchport
no ip address
SW1# show running-config interface gigabitethernet1/0/1
interface GigabitEthernet1/0/1
no switchport
ip address 10.1.1.1 255.255.255.252
channel-group 5 mode activeWhat has to be corrected?
That’s 2 of the full CCNA bank.
Keep going free: 10 questions per certification in bank practice, with no account.
Continue practicingRead the sources
These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.