Two negotiation protocols and a third option
| Point of comparison | LACP | PAgP | Mode on |
|---|---|---|---|
| Standard | IEEE 802.1AX (formerly 802.3ad) | Cisco proprietary | No protocol at all |
| Mode that starts negotiation | active | desirable | None |
| Mode that only answers | passive | auto | None |
| Works with other vendors | Yes | No | Yes, if both ends are static |
| Named in the exam topics | v1.1 2.4 and v2.0 2.1.c | Neither version | Not by name |
Topic IDs from Cisco’s v1.1 and v2.0 topic lists, linked under the sources.
What the bundle buys and where it sits
An EtherChannel turns parallel physical links into one logical Port-channel interface. Spanning tree treats the bundle as a single port, so the parallel links forward together instead of all but one going to discarding; that is the link back to the STP root bridge and port roles page.
The negotiation protocol is there so both ends agree before a member port starts forwarding into the channel. Mode on skips that agreement: the ports join the channel whether or not the other side has done the same.
v1.1 topic 2.4 covers Layer 2 and Layer 3 channels. In a Layer 2 channel the Port-channel interface holds the switchport settings, access or trunk, and the member ports follow them. In a Layer 3 channel the Port-channel is a routed interface: no switchport on the bundle, and the IP address goes on the Port-channel, never on a member.
LACP is the protocol the blueprint names. PAgP stays on the map because its mode keywords share the same channel-group command, which makes them easy to confuse with LACP’s. PortFast and the STP protections sit beside it on the Rapid PVST+ and EtherChannel study area.
The mode matrix
| SW1 ↓ / SW2 → | active | passive | desirable | auto | on |
|---|---|---|---|---|---|
| active | LACP bundle | LACP bundle | No bundle | No bundle | No bundle |
| passive | LACP bundle | No bundle | No bundle | No bundle | No bundle |
| desirable | No bundle | No bundle | PAgP bundle | PAgP bundle | No bundle |
| auto | No bundle | No bundle | PAgP bundle | No bundle | No bundle |
| on | No bundle | No bundle | No bundle | No bundle | Static bundle |
Read the diagonal first: only the two listening modes fail against themselves. Every cell that mixes protocol families fails, and on only pairs with on.
Building and checking an LACP channel
Two uplinks bundled as Port-channel 7, then the summary line that proves it.
SW1(config)# interface range GigabitEthernet1/0/1 - 2SW1(config-if-range)# channel-group 7 mode activeSW1(config-if-range)# exitSW1(config)# interface Port-channel7SW1(config-if)# switchport mode trunkSW1(config-if)# endSW1# show etherchannel summary...Group Port-channel Protocol Ports------+-------------+-----------+-----------------------------------------------7 Po7(SU) LACP Gi1/0/1(P) Gi1/0/2(P)In the summary legend, S is Layer 2, U is in use and P is bundled in the port-channel. A member flagged I is stand-alone and s is suspended; either means the negotiation or the member settings need a second look.
Frames on LACP vs PAgP modes
Each scenario gives you the two ends of a link. Place the pair on the mode matrix above, then decide which option describes the outcome and its cause.
Practice frames written by our editors for study, not Cisco items. The 200-301 exam itself mixes multiple choice, drag-and-drop and lab-style items.
Frame 001 of 006 · 0 answered · 0 ok
Keys
1–5 or A–E pick an option (on choose-N frames they toggle; then Check answer) · ← → previous / next frame · ↑ ↓ move in the frame list
- Frame 001 of 006
Which EtherChannel negotiation protocol is an IEEE standard?
Pick an option. The verdict shows here; open the note under any option to see why.
Note on A
Correct: LACP is the IEEE standard (802.3ad, now 802.1AX), so it can bundle links between switches from different vendors.
Note on B
STP is an IEEE standard too, but it prevents loops; it does not negotiate EtherChannels.
Note on C
UDLD is a Cisco protocol that detects one-way links; it has no part in bundling ports.
Note on D
PAgP does negotiate EtherChannels, but it is Cisco-proprietary rather than an IEEE standard.
Best answer: A · why
Two protocols can negotiate an EtherChannel. LACP is defined by IEEE (originally 802.3ad, now 802.1AX) and uses the active and passive modes. PAgP is Cisco-proprietary and uses desirable and auto. Mode on builds the bundle with no negotiation at all. STP handles loops and UDLD detects unidirectional links; neither one forms a bundle.
- Frame 002 of 006
Which command would you use to configure a port to participate in LACP negotiation and actively initiate negotiations?
Pick an option. The verdict shows here; open the note under any option to see why.
Note on A
Correct: active mode sends LACP packets to start negotiation, so the bundle forms with a far end that is active or passive.
Note on B
Passive mode only answers LACP packets and never starts negotiation, so two passive ends never form a bundle.
Note on C
Auto is a PAgP mode, and it waits for the other side instead of starting negotiation.
Note on D
Mode on forces the port into the bundle with no LACP or PAgP negotiation at all.
Best answer: A · why
channel-group <n> mode sets both the protocol and which side starts negotiation. LACP uses active (initiates) and passive (responds). PAgP uses desirable (initiates) and auto (responds). on forms a static EtherChannel with no protocol, so both sides must be on. Passive with passive, or auto with auto, never forms a bundle.
- Frame 003 of 006
What is the primary purpose of Link Aggregation Control Protocol (LACP)?
Pick an option. The verdict shows here; open the note under any option to see why.
Note on A
Correct: LACP exchanges messages between the two ends to agree which links join the bundle and keeps checking that they still belong.
Note on B
Loop prevention is spanning tree’s job; STP sees an EtherChannel as one logical link, but LACP itself blocks nothing.
Note on C
Neighbor discovery is handled by CDP and LLDP, not by the link-aggregation protocol.
Note on D
LACP carries no authentication; port access control is handled by 802.1X and AAA.
Best answer: A · why
LACP (IEEE 802.1AX, formerly 802.3ad) lets two devices negotiate an EtherChannel. They exchange LACP data units, check that the member links have compatible settings, add them to the bundle and drop any link that stops responding. Loop prevention, neighbor discovery and port authentication are the jobs of spanning tree, CDP/LLDP and 802.1X.
- Frame 004 of 006
SW1 has ‘channel-group 1 mode active’ on Gi0/1 and Gi0/2. SW2 has ‘channel-group 1 mode passive’ on the two ports that connect to them. Speed, duplex, trunk and VLAN settings match on all four ports. What is the result?
Pick an option. The verdict shows here; open the note under any option to see why.
Note on A
Correct. An active port sends LACPDUs and a passive port responds to them, so active with passive is enough to negotiate the bundle.
Note on B
Only one end has to start the exchange. Active with active also works, but active with passive forms the bundle too.
Note on C
Passive is an LACP mode. The PAgP modes are desirable and auto, so passive cannot be mixed up with PAgP here.
Note on D
A bundle with no negotiation needs mode on at both ends. Active and passive exchange LACPDUs, so the bundle is negotiated, not static.
Best answer: A · why
LACP (IEEE 802.1AX) has two negotiating modes. An active port sends LACPDUs to start negotiation; a passive port does not start but responds when it receives LACPDUs. A bundle forms when at least one end is active: active with active or active with passive. Passive with passive never forms, because neither side speaks first. Mode on is a separate, unnegotiated setting that sends no LACPDUs at all. Here SW1 is active and SW2 is passive, and the member ports match, so LACP negotiates the EtherChannel. Source: IEEE 802.1AX-2020 and Cisco’s EtherChannel configuration example.
- Frame 005 of 006
An engineer is checking channel-group modes on pairs of Cisco switches whose member ports otherwise match. Which pair of modes fails to form an EtherChannel?
Pick an option. The verdict shows here; open the note under any option to see why.
Note on A
Desirable sends PAgP packets and auto answers them, so this pair negotiates a channel.
Note on B
Mode on at both ends builds the channel unconditionally, without PAgP or LACP, so this pair does form a bundle.
Note on C
Both ends send PAgP packets and both answer, so two desirable ends form the channel.
Note on D
Correct. Auto only answers PAgP packets and never sends them first, so two auto ends wait for each other and no channel forms.
Best answer: D · why
PAgP, Cisco’s own bundling protocol, mirrors LACP’s two modes: desirable starts negotiation by sending PAgP packets, and auto only responds. A channel forms when at least one end is desirable, so desirable with desirable and desirable with auto work, while auto with auto does not, because neither end speaks first. Mode on skips negotiation entirely and must be set on both ends; on with on forms a static bundle. PAgP is not named in the current exam topics, but the same start-or-respond logic is what the exam tests for LACP active and passive. Source: Cisco’s EtherChannel configuration example (mode table).
- Frame 006 of 006
SW1’s member ports use ‘channel-group 5 mode on’. The matching ports on SW2 use ‘channel-group 5 mode active’. What is the result?
Pick an option. The verdict shows here; open the note under any option to see why.
Note on A
Active only works if the far end speaks LACP. A port in mode on never answers LACPDUs, so there is nothing for SW2 to negotiate with.
Note on B
Correct. Mode on runs no protocol, so SW2’s LACPDUs go unanswered. SW2 cannot negotiate, and its ports stay out of a working bundle.
Note on C
Mode on has no fallback. It uses neither PAgP nor LACP and simply forces the ports into a channel on its own side.
Note on D
IOS never changes a configured channel mode by itself. SW1 stays in mode on until someone reconfigures it.
Best answer: B · why
Mode on forces ports into an EtherChannel with no negotiation protocol, so it neither sends nor answers LACPDUs or PAgP packets. It only works when the other end is also set to on. With mode on facing LACP active, SW2 sends LACPDUs and hears nothing back, so it never negotiates a bundle; depending on the platform its ports are suspended or run as individual links. SW1 meanwhile treats its side as a channel, and that mismatch can cause loops or err-disabled ports. The fix is to use on at both ends or LACP active or passive at both ends. Source: IEEE 802.1AX-2020 and Cisco’s EtherChannel configuration example.
Further along the access layer
The same access-layer map continues into the wireless edge, where the question changes from how links bundle to how clients prove who they are. WPA2 vs WPA3 covers PSK, SAE and 802.1X.
References
- [1]Cisco Learning Network: CCNA v1.1 exam topicsChecked October 29, 2026.
- [2]Cisco Learning Network: CCNA v2.0 exam topicsChecked October 29, 2026.