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title: Port Clustering and Aggregation
tags: Cisco IOS, networking, manual, reference, router, switch, technical
---

<header>
<h6>Port Clustering and Aggregation</h6>

> [toc]
</header>
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# EtherChannel Configuration

## Link Aggregation Control Protocol

**Configure the ports Fa0/1 and Fa0/2 as members of channel-group 1, using LACP unconditionally.**

S1(config)# interface range FastEthernet 0/1 - 2
S1(config-if-range)# channel-group 1 mode active
! Creating a port-channel interface Port-channel 1
S1(config)# interface port-channel 1
S1(config)# switchport mode trunk
S1(config)# switchport trunk allowed vlan 1,2,20
S1(config)# end
S1# 
S1# show interfaces port-channel 1
! Port-channel1 is up, line protocol is up (connected)
!   Hardware is EtherChannel, address is c07b.bcc4.a981 (bia ! c07b.bcc4.a981)
!   MTU 1500 bytes, BW 200000 Kbit/sec, DLY 100 usec,
!      reliability 255/255, txload 1/255, rxload 1/255
  (output omitted)
S1# 
S1# show etherchannel summary
  (output omitted)
! Number of channel-groups in use: 1
! Number of aggregators:           1
! Group  Port-channel  Protocol    Ports
! ------+-------------+-----------+-----------------------------------------------
! 1      Po1(SU)         LACP      Fa0/1(P)    Fa0/2(P)

## Port Modes: <abbr title="Port Aggregation Protocol">PAgP</abbr> vs <abbr title="Link Aggregation Control Protocol">LACP</abbr>
- **PAgP - `desirable/auto`**
- **LACP - `active/passive`**

## Troubleshooting Common Issues

* Assigned ports in the EtherChannel are not part of the same VLAN, or not configured as trunks. Ports with different native VLANs cannot form an EtherChannel.
* Trunking was configured on some of the ports that make up the EtherChannel, but not all of them. It is not recommended that you configure trunking mode on individual ports that make up the EtherChannel. When configuring a trunk on an EtherChannel, verify the trunking mode on the EtherChannel.
* If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the **auto** or **desirable** mode.
* The dynamic negotiation options for PAgP and LACP are not compatibly configured on both ends of the EtherChannel.

S1# show etherchannel summary
S1# show run | begin interface port-channel

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