Categories R&S

L2 Technologies – Etherchannel

Today’s post will be about Etherchannel.

That’s a quite simple topic.

 

We will keep the same topology. We have an etherchannel between SW10 and SW11.

Let’s play around with it.

 

L2 Technologies – Etherchannel – Physical network diagram

L2 technologies - Etherchannel

 

L2 Technologies – Etherchannel  – configuration:

L2 Technologies – Etherchannel  – Static Layer 2 EtherChannels:

 

The on mode forces a port to join an EtherChannel without negotiations.

Port-channel have to be configured the same way on both side.

Usually I will use the interface range command.

SW10(config)#int range Eth 0/1 , Eth 0/2
SW10(config-if-range)#channel-group 10 mode on
Creating a port-channel interface Port-channel 10

SW11(config)#int range Eth 0/1 , Eth 0/2
SW11(config-if-range)#channel-group 10 mode on
Creating a port-channel interface Port-channel 10

 

To verify the port-channel, you use the following command.

SW10#sh etherchannel sum
Flags:  D - down        P - bundled 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
Number of channel-groups in use: 1
Number of aggregators:           1
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
10     Po10(SU)         -        Et0/1(P)    Et0/2(P)

 

L2 Technologies – Etherchannel  – PAgP:

The Port Aggregation Protocol (PAgP) is a Cisco-proprietary protocol that can be run only on Cisco switches.

 

Ports can form an EtherChannel when they are in different PAgP modes as long as the modes are compatible. For example:

A port in the desirable mode can form an EtherChannel with another port that is in the desirable or auto mode.

A port in the auto mode can form an EtherChannel with another port in the desirable mode.

SW10(config-if-range)#int range Et0/1 , Et0/2
SW10(config-if-range)#channel-group 10 mode desirable

SW11(config-if-range)#int range Eth 0/1 , Eth 0/2
SW11(config-if-range)#channel-group 10 mode auto

 

Let’s verify, both interfaces are bundle and the protocol is listed as PAgP.

SW10#sh etherchannel sum
Flags:  D - down        P - bundled 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
Number of channel-groups in use: 1
Number of aggregators:           1
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
10     Po10(SU)        PAgP      Et0/1(P)    Et0/2(P)

 

L2 Technologies – Etherchannel  – LACP:

The LACP is defined in IEEE 802.3ad and enables Cisco switches to manage Ethernet channels between switches that conform to the IEEE 802.3ad protocol.

 

Ports can form an EtherChannel when they are in different LACP modes as long as the modes are compatible. For example:

A port in the active mode can form an EtherChannel with another port that is in the active or passive mode.

A port in the passive mode cannot form an EtherChannel with another port that is also in the passive mode because neither port starts LACP negotiation.

SW10(config)#int range Et0/1 , Et0/2
SW10(config-if-range)#channel-group 10 mode active

SW11(config-if)#int range Eth 0/1 , Eth 0/2
SW11(config-if-range)#channel-group 10 mode passive
SW10#sh etherchannel sum
Flags:  D - down        P - bundled 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
Number of channel-groups in use: 1
Number of aggregators:           1
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
10     Po10(SU)        LACP      Et0/1(P)    Et0/2(P)

 

L2 Technologies – Etherchannel  – Load Balancing:

The load balancing method can be different depending of the switch platform.

Different load-balancing methods have different advantages

The choice of a particular method should be based on the position of the switch in the network and the kind of traffic that needs to be load-distributed.

 

Here is the command to change from the default source-MAC address of the incoming packet.

SW10(config)#port-channel load-balance ?
  dst-ip       Dst IP Addr
  dst-mac      Dst Mac Addr
  src-dst-ip   Src XOR Dst IP Addr
  src-dst-mac  Src XOR Dst Mac Addr
  src-ip       Src IP Addr
  src-mac      Src Mac Addr

 

That’s all for etherchannel.

In the next post I will have a look at spanning-tree.

 

 

 

Thank you for reading.

 

 

L2 Technologies – Etherchannel

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