Question
Which of the following combinations of PAgP modes prevents etherChannel from forming?
- auto/desirable
- desirable/desirable
- desiravle/auto
- auto/auto
- See answers
- (4)
Commentary
Combination of EtherChannel (PAgP) operating modes
Cisco’s proprietary EtherChannel negotiation mechanism PAgP has two modes to set up the interface.
- Desirable
Enable PAgP unconditionally. Start sending negotiation messages to other ports. - Auto
Enable PAgP only when a PAgP device is detected. In other words, it waits for an on-the-other request and responds to a request for PAgP negotiation. This reduces the transmission of PAgP packets.
Auto and Auto do not start negotiating PAgP from the above mode.
A combination of Desirable/Desirable and Desirable/Auto is required to use PAgP.
Therefore, the combination that prevents formation is ④.