What is the maximum number of physical link we can bind to a ether-channel and port-channel

[dipak jaiswal]

Hi,

I was studying about port-channel & ether-channel and found that, it can be bind up-to 8 ports. So maximum number, we can have of 8 ports or more ? 

For binding we should have minimum of 2 ports or 1 ports will work ? For load-balancing purpose, is the port no. would be in a bundle of 2,4 and 8 ?

Thanks

[nkarthikeyan]

Hi Dipak,

You can have maximum of 8 ports configured in a ether-channel / port-channel. for load balacing scenario you can refer the below mentioned table.

Number of Ports in the EtherChannel	Load Balancing ratio between Ports
8	1:1:1:1:1:1:1:1
7	2:1:1:1:1:1:1
6	2:2:1:1:1:1
5	2:2:2:1:1
4	2:2:2:2
3	3:3:2
2	4:4

Regards

Karthik

[dipak jaiswal]

Hi Kathik,

I have gone through one document. It's saying the below mentioned things :

Jun 7, 2012 9:36 PM (in response to Sarabjit)

Re: What is the maximum number of etherchannels we can have?

The maximum number of Etherchannels varies from platform to platform. The maximum number of ports in an etherchannel is either 8 ro 16 depending on the platform. The minimum number of ports in an etherchannel bundle is 1.

Jun 8, 2012 1:27 AM (in response to Sarabjit)

Re: What is the maximum number of etherchannels we can have?

Etherchannels is a Cisco term. Other vendors call them 802.3ad trunks. It's common to see something like this in datasheets:

48 ports 10/100/1000 Mbit/s

802.3ad:

• Maximum of 32 groups
• Maximum of 8 ports per group

The document url is https://learningnetwork.cisco.com/thread/43680

The another document says the below mentioned things :

Matrix of Load Balancing Methods

This matrix consolidates the load balancing methods that this document describes:

Platform	Address Used in XOR	Source-Based?	Destination-Based?	Source-Destination-Based?	Load Balancing Method—Configurable/Fixed?
6500/6000	Layer 2, Layer 3 addresses, Layer 4 information, or MPLS information2	Yes	Yes	Yes	Configurable
5500/5000	Layer 2 address only	—	—	Yes	Cannot change the method
4500/4000	Layer 2, Layer 3 addresses, or Layer 4 information	Yes	Yes	Yes	Configurable
2900XL/3500XL	Layer 2 address only	Yes	Yes	—	Configurable
3750/3560	Layer 2 or Layer 3 address only	Yes	Yes	Yes	Configurable
2950/2955/3550	Layer 2 address only1	Yes	Yes	—1	Configurable
1900/2820	These platforms use a special method of load balancing. See theCatalyst 1900/2820 section for details.
8500	Layer 3 address only	—	—	Yes	Cannot change the method

¹ For the 3550 series switch, when source-MAC address forwarding is used, load distribution based on the source and destination IP address is also enabled for routed IP traffic. All routed IP traffic chooses a port based on the source and destination IP address.

² For the 6500 series switches that run Cisco IOS, MPLS layer 2 information can also be used for load balancing MPLS packets.

The document url is http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/12023-4.html

Another document says the below mentioned things for load-balancing :

inally, here is full list of valid load-distribution methods:

•dst-ip—Load distribution on the destination IP address

•dst-mac—Load distribution on the destination MAC address

•dst-port—Load distribution on the destination TCP/UDP port

•src-dst-ip—Load distribution on the source XOR destination IP address

•src-dst-mac—Load distribution on the source XOR destination MAC address

•src-dst-port—Load distribution on the source XOR destination TCP/UDP port

•src-ip—Load distribution on the source IP address

•src-mac—Load distribution on the source MAC address

•src-port—Load distribution on the source port

The document url is https://learningnetwork.cisco.com/thread/63064

Please suggest.

[nkarthikeyan]

Hi Dipak,

Yeah.... It depends on platform. But having 1 interface bundled in etherchannel is of no meaning. Actual purpose of etherchannel is to bundle two or more interfaces tagged. But you can have 1 interface also configured for ether-channel.

Also the maximum number of groups you can create is purely depends on the platform model. sat 6500 series can have maximum of 64 channel-groups. 3560 can have 48 channel-groups......

I am sorry for that we can have 16 port also tagged to a single ether-channel group. I will check even if we can have more.

For load balancing you should have the bundle in even number to do fair loadbalancing.

Regards

Karthik

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Most Cisco devices, that support port-channels, support up to 8 ports; some (as you've noted in your 2nd post) can support more.  (Also, there's a limit to how many port-channels are supported per device.)

Port-channels can contain from 1 to max number of links.  As the other poster has noted, a port-channel of 1 doesn't make much sense, however, you might have a port-channel with only one member link if other member link(s) have failed or perhaps you're planning to add another link but don't have all the necessary hardware when you first define the port-channel.

Load balancing tends to work best on binary number of port-channel members, but some later Cisco devices have improved load balancing across non-binary number of port-channel members, e.g. the sup2T.

Load balancing also depends on the attributes of the traffic and the hashing algorithm being used.

[dipak jaiswal]

Hi Joseph,

I have a query related to load-balancing. As the load-balancing can be done on the basis the of nos. of port being bundle on the ether-channel/port-channel as well as on the basis of layer 2 or layer 3 addresses. If somebody ask me, how the load-balancing done on the ether-channel/port-channel, what should i say ?

Can i say both the concepts(i.e. layer 2 or layer 3 addresses and nos. of port being bundle in a channel).

What is the default load-balancing method at ether-channel and port-channel ?

Thanks for clearing the concept of nos. of physical link bundling.

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Last question first, default load balancing algorithm depends on the platform.

For your first question, load balancing works by using whatever load balancing algorithm is in effect to create a port member number, and then it sends the traffic to that port member.

For example, if you divide the source MAC by 8, the reminder will always be a number between 0 and 7; add 1 and that will be your port number.  Or you might divide destination IP by 8, etc.

Also say, if you had less than 8 ports, where does the "extra" port traffic go.  Well, you just start with the first available port.  So as Karthik posted, for 7 ports, port 8 traffic goes to port 1, which is why port one has 2x the traffic of all the other ports.  If only 6 ports, port 7 goes to port 1, port 8 goes to port 2, as seen in Karthik's distribution for 6 ports; and so on.