Last Updated on August 6, 2021 by Admin 3
You want to establish an EtherChannel between SwitchA and SwitchB.
Which of the following modes can you configure on both of the switches to establish the EtherChannel over PAgP? (Select the best answer.)
- on
- passive
- active
- desirable
- auto
You can configure both switches to operate in desirable mode to establish the EtherChannel over Port Aggregation Protocol (PAgP). Alternatively, you can set one switch to auto and the other switch to desirable.
PAgP is a Ciscoproprietary protocol that groups individual physical PAgPconfigured ports into a single logical link, called an EtherChannel. The ports that constitute an EtherChannel are grouped according to various parameters, such as hardware, port, and administrative limitations. Once PAgP has created an EtherChannel, it adds the EtherChannel to the spanning tree as a single switch port. Because PAgP is a Cisco-proprietary protocol, it can be used only on Cisco switches.
Link Aggregation Control Protocol (LACP) is a newer, standardsbased alternative to PAgP that is defined by the Institute of Electrical and Electronics Engineers (IEEE) 802.3ad standard. LACP is available on switches newer than the Catalyst 2950 switch, which offers only PAgP. Like PAgP, LACP identifies neighboring ports and their group capabilities; however, LACP goes further by assigning roles to the EtherChannel’s endpoints. Because LACP is a standardsbased protocol, it can be used between Cisco and nonCisco switches.
The following table displays the channelgroup configurations that will establish an EtherChannel:
The channelgroup command configures the EtherChannel mode. The syntax of the channelgroup command is channelgroup number mode {on | active | passive | {auto | desirable} [nonsilent]}, where number is the port channel interface number. The on keyword configures the channel group to unconditionally create the channel with no LACP or PAgP negotiation.
The active and passive keywords can be used only with LACP. The active keyword configures the channel group to actively negotiate LACP, and the passive keyword configures the channel group to listen for LACP negotiation to be offered. Either or both sides of the link must be set to active to establish an EtherChannel over LACP? setting both sides to passive will not establish an EtherChannel over LACP.
The auto, desirable, and nonsilent keywords can be used only with PAgP. The desirable keyword configures the channel group to actively negotiate PAgP, and the autokeyword configures the channel group to listen for PAgP negotiation to be offered. Either or both sides of the link must be set to desirable to establish an EtherChannel over PAgP; setting both sides to auto will not establish an EtherChannel over PAgP. The optional nonsilent keyword requires that a port receive PAgP packets before the port is added to the channel.