etherchannel

[nettuno8_20111]

hi I have 2 catalist 2960 10/100 switches and they are connected to each other with 8 cables with the etherchannel mode and with a bandwidth less than 800mbps, because I know to have 800mbps effective the etherchannel mode must be configured in a certain way. what configuration can I give to etherchannel to have 800mbps?

[Reza Sharifi · Accepted solution]

Hi,

There is no special configuration needed. Once you configure the Etherchannel with all 8 ports in it, if you issue the command "sh interface po x" you should see the bandwidth of 800Mb. 

HTH

[balaji.bandi · Accepted solution]

There is no special configuration required -

simple config both the side :

interface range fastEthernet x/x -y
channel-group 1 mode active

#interface Port-channel 1
#switchport trunk encapsulation dot1q 
#switchport mode trunk

show etherchannel 1 port-channel 

Load balance check here :

https://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/12023-4.html

[Joseph W. Doherty · Accepted solution]

First with eight 100 Mbps links bound in Etherchannel, you have 800 Mbps aggregate bandwidth, but a single flow is still limited to 100 Mbps.

Second, depending on the LB algorithm being used, and the attributes of your traffic, all flows, worst case, could be directed to the same link.  Even with an "ideal" LB algorithm choice, you might not ever see full aggregate bandwidth utilization, because flows are directed to specific links based on the traffic flow's attributes, not actual link loading.

For example, with just dual links, in Etherchannel, you likely will not see utilization above 75% of the dual link aggregate.  Why?  Well if you start with just one flow, it uses just one link.  When you add the second flow, assuming even really random link selection, there's a 50/50 chance whether it will also use the concurrent flow's link or the one being unused.  I.e. either half or all the Etherchannel bandwidth.  On average, 3/4 of the Etherchannel bandwidth will be used.

Ideally, what you want to configure is the "best" LB algorithm the platform supports for your traffic's attributes.  Often the "best" choice, on many platforms, is src-dst-IP.