EtherChannel PAgP and LACP modes

1. EtherChannel PAgP and LACP
modes

2.  EtherChannel is a port link aggregation technology
developed by Cisco, which provides fault-tolerant high-
speed links between Switches, Routers, and Servers.
 EtherChannel technology allows multiple physical
Ethernet links (Fast EtherNet or Gigabit Ethernet) to
combine into one logical channel.

3.  There are two protocols used for negotiating
EtherChannel and Link Aggregation. We can configure
Etherchannel in three ways in Cisco Switches.
1. Port Aggregation Protocol (PAgP) - Cisco Proprietary
protocol
2. IEEE Link Aggregation Protocol (LACP) - Industry
Standard
3. Manual Etherchannel Configuration - Without using
any negotiation protocol listed above
 Port Aggregation Protocol (PAgP) has two Channel
modes and they are "Desirable" and "Auto".
 Link Aggregation Control Protocol (LACP) has two
Channel modes and they are "Active" and "Passive".

4. Port Aggregation Protocol (PAgP)
Modes
 Auto Mode: Auto mode in Port Aggregation Protocol (PAgP))
does not initiate the negotiation, but responds to Port
Aggregation Protocol (PAgP) packets initiated by other end.
Auto mode in Port Aggregation Protocol (PAgP) does not
start Port Aggregation Protocol (PAgP) packet negotiation
 Desirable mode: Desirable mode in Port Aggregation
Protocol (PAgP) initiates the negotiation and tries to form
EtherChannel with other end.
 If you are using Port Aggregation Protocol
(PAgP) for EtherChannel negotiation, EtherChannel will be
formed only if two ends are configured under following
modes.
Desirable Auto
Desirable Yes Yes
Auto Yes No

5. Link Aggregation Control Protocol
(LACP)
 Active Mode: Active Mode in Link Aggregation Control
Protocol (LACP) initiates the negotiation and tries to
form EtherChannel with other end.
 Passive Mode: Passive Mode in Link Aggregation
Control Protocol (LACP) does not initiate the
negotiation, but responds to Link Aggregation Control
Protocol (LACP) packets initiated by other end.
Passive Mode in Link Aggregation Control Protocol
(LACP) does not start Link Aggregation Control
Protocol (LACP) packet negotiation.
Active Passive
Active Yes Yes
Passive Yes No

6. EtherChannel "on" mode
 EtherChannel "on" mode makes the interface into
an EtherChannel without any negotiation protocols like Port
Aggregation Protocol (PAgP) or Link Aggregation Control
Protocol (LACP). When using a EtherChannel "on" mode,
EtherChannel will be created only when another interface
group in EtherChannel "on" mode.
 Switch interfaces exchange Port Aggregation Protocol
(PAgP) packets only with partner interfaces configured in the
auto or desirable modes. Switch interfaces exchange Link
Aggregation Control Protocol (LACP) packets only with
partner interfaces configured in the active or passive modes.
Interfaces configured in the "on" Channel mode do not
exchange Port Aggregation Protocol (PAgP) or Link
Aggregation Control Protocol (LACP).