Etherchannel is useful in a scenario which you have need to have additional bandwidth particularly between switches hosting servers;

On this page i will provide an example on three (3) Cisco Etherchannel modes

Note: All interface need to match the following to successfully join the Etherchannel

  • Speed
  • Duplex
  • Medium

Etherchannel

3 Cisco Etherchannel Mode

  • Static
  • Cisco Proprietary Implementation
  • Industry standard

Mode 1: Static Etherchannel


SW1

interface range FastEthernet0/13 – 15
  switchport mode dynamic desirable
  channel-group 12 mode on

SW2

interface range FastEthernet0/13 – 15
  switchport mode dynamic desirable
  channel-group 12 mode on

Verification

SW1#show etherchannel summary
Flags:  D - down        P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3      S - Layer2
U - in use      f - failed to allocate aggregator
u - unsuitable for bundling
w - waiting to be aggregated
d - default port

 Number of channel-groups in use: 1
Number of aggregators:           1
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-------------------
12     Po12(SU)         -        Fa0/13(P)   Fa0/14(P)   Fa0/15(P) 
SW2#show etherchannel summary
Flags:  D - down        P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3      S - Layer2
U - in use      f - failed to allocate aggregator
u - unsuitable for bundling
w - waiting to be aggregated
d - default port

 Number of channel-groups in use: 1
Number of aggregators:           1
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-------------------
12     Po12(SU)         -        Fa0/13(P)   Fa0/14(P)   Fa0/15(P) 

You will see on this mode the protocol field of the Etherchannel is blank.

Mode 2: Cisco Proprietary Implementation (PAgP)


SW1

interface Range FastEthernet0/13 - 15
 switchport mode dynamic desirable
 channel-group 12 mode desirable

SW2

interface Range FastEthernet0/13 - 15
 switchport mode dynamic desirable
 channel-group 12 mode desirable

Verification

SW1(config-if)#do show ether sum
Flags:  D - down        P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3      S - Layer2
U - in use      f - failed to allocate aggregator
u - unsuitable for bundling
w - waiting to be aggregated
d - default port

 Number of channel-groups in use: 3
Number of aggregators:           3
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-------------------
12     Po12(SU)        PAgP      Fa0/13(P)   Fa0/14(P)   Fa0/15(P)   
SW2(config-if-range)#do show ether sum
Flags:  D - down        P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3      S - Layer2
U - in use      f - failed to allocate aggregator
u - unsuitable for bundling
w - waiting to be aggregated
d - default port

 Number of channel-groups in use: 2
Number of aggregators:           2
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-------------------
1      Po1(SD)         PAgP      Fa0/13()    Fa0/14()    Fa0/15()


You will see on this mode that the protocol field of the Etherchannel is now PAgP.

Two configuration variation could build the PAgP mode

  • Desirable + Desirable
  • Desirable + Auto

Mode 3: Industry Standard Implementation (LACP)


SW1

interface Range FastEthernet0/13 - 15
 switchport mode dynamic desirable
 channel-group 12 mode active
SW2

interface Range FastEthernet0/13 - 15
 switchport mode dynamic desirable
 channel-group 12 mode active

Verification

SW1(config-if-range)#do sho ether sum
Flags:  D - down        P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3      S - Layer2
U - in use      f - failed to allocate aggregator
u - unsuitable for bundling
w - waiting to be aggregated
d - default port

 Number of channel-groups in use: 1
Number of aggregators:           1
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-------------------
1      Po1(SU)         LACP      Fa0/13(P)   Fa0/14(P)   Fa0/15(P) 
SW2(config-if-range)#do show ether sum
Flags:  D - down        P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3      S - Layer2
U - in use      f - failed to allocate aggregator
u - unsuitable for bundling
w - waiting to be aggregated
d - default port

 Number of channel-groups in use: 1
Number of aggregators:           1
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-------------------
1      Po1(RU)         LACP      Fa0/13(P)   Fa0/14(P)  Fa0/15(P)

You will see on this mode that the protocol field of the Etherchannel is now LACP.

Two configuration variation could build the LACP mode

  • Active + Active
  • Active + Passive

 

As stated above we could do 3 Etherchannel configuration mode depending on our network requirements and with addition two variation for dynamic etherchannel.

Cisco Etherchannel Mode
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