Link Aggregation Control Protocol (LACP) is another option when configuring EtherChannels
- LACP is an open protocol adhering to the 802.3ad standard
- It uses the multicast address of 01-80-c2-00-00-02
- Channel mode must be set to "active" or "passive" to specify an LACP port-channel
- Active - Enable LACP unconditionally
- Passive - Enable LACP only if LACP device is detected
- In other words, active sends requests and passive only listens for requests. If both sides are passive than an LACP link will not form.
- At least one side must be active for an LACP link to form
- During LACP negotiation, it ensures all links have the same configuration, speed and duplex else they aren't allowed to participate in the LACP channel. This prevents loops.
- Maximum number of links in port-channel is 8
- It is recommended to configure 1, 2, 4 or 8 ports in the EtherChannel
- As opposed to PAgP, LACP does support participating interfaces being on different physical switches. If you are using VSS, or stacked switches, or device redundancy through virtualization, then LACP is your best choice for EtherChannels.
PacketTracer Lab: CCNA-2.9.c-How-to-configure-LACP-Port-Channels.pkt
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