350-401 · Question #748
Refer to the exhibit. Traffic is not passing between SW1 and SW2. Which action fixes the issue?
The correct answer is C. Configure PAgP mode on S1 to desirable.. To resolve an EtherChannel issue between SW1 and SW2 using PAgP, configuring SW1's PAgP mode to desirable will ensure it actively attempts to form the EtherChannel, which is necessary for PAgP operation.
Question
Exhibits
Options
- AConfigure LACP mode on S1 to passive.
- BConfigure switch port mode to ISL on S2.
- CConfigure PAgP mode on S1 to desirable.
- DConfigure LACP mode on S1 to active.
How the community answered
(43 responses)- A12% (5)
- B5% (2)
- C77% (33)
- D7% (3)
Why each option
To resolve an EtherChannel issue between SW1 and SW2 using PAgP, configuring SW1's PAgP mode to `desirable` will ensure it actively attempts to form the EtherChannel, which is necessary for PAgP operation.
LACP (Link Aggregation Control Protocol) is a distinct protocol from PAgP; configuring LACP modes would not resolve an EtherChannel issue rooted in PAgP misconfiguration.
ISL (Inter-Switch Link) is a deprecated, Cisco-proprietary trunking encapsulation and is not directly related to EtherChannel negotiation or widely used on modern switches for this purpose.
PAgP (Port Aggregation Protocol) requires at least one side of an EtherChannel to be in `desirable` mode for active negotiation to occur and form a bundled link. If the exhibit implies a PAgP misconfiguration preventing traffic, setting SW1 to `desirable` will trigger the negotiation with SW2.
LACP is a different EtherChannel negotiation protocol; if the issue is with PAgP configuration, configuring LACP on S1 would not solve the problem.
Concept tested: PAgP EtherChannel negotiation modes
Source: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_44_se/configuration/guide/scg/sweth.html#wp1019080
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