Port-channel question

[raulzulueta]

I am configuring some new c6509-e switches for my network and get this error message when I configure a port-channel.

What does this really mean and how do I configure port-channel on ws-x6548-ge-45af line cards?

CAPI_EC-4-GROUP_RATE_LIMITED   : Adding interfaces of the same port-group (%d-%d)  on %s to an etherchannel will not increase the channel throughput!

Explanation   Because ports on the indicated  slot use oversubscription, the total throughput of the port  channel is limited by port-group.

Recommended Action   If more throughput is  required, either use ports from a card that does not use  oversubscription, or use ports from different cards or port-groupings on  oversubscribed cards. For  example, if the card has 48 ports in groups of eight, you can select  ports 1, 9, 17, 25, 33, and 41 for  the same port-channel.

Thanks.

[Jason Masker · Accepted solution]

The error message is informing you that the oversubscription of your line card will prevent you from gaining any throughput from aggregating the links you specified.

Basically the ports you tried to aggregate share resources. If you are merely creating the port channel for physical link redundancy you can safely ignore the error. Otherwise, if increased throughput is desired, you should bond ports from different groups together. On the 6548 ports 1-8 share bandwidth as do ports 9-16 and so on.

Jason

[raulzulueta]

So you are saying I am restricted do a grouping of ports 1-8, 9-16, 17-24, 25-32, 33-40, 41-48 only. If I only need 4 ports then I will use ports 1-4 or if I need 6 I will then use ports 1-6 or 9-14, is that how it will happen?

[Jon Marshall · Accepted solution]

raulzulueta wrote:
So you are saying I am restricted do a grouping of ports 1-8, 9-16, 17-24, 25-32, 33-40, 41-48 only. If I only need 4 ports then I will use ports 1-4 or if I need 6 I will then use ports 1-6 or 9-14, is that how it will happen?

No that's not what Jason meant. Basically if you want the etherchannel purely for redundancy then you can use any of the ports on the module. If however you want the etherchannel for throughput as well ie. you want the 4Gbps throughput then you would need to do make sure each of the 4 interfaces is from a separate port group on the module. So for example you could could create your etherchannel by using -

ports 4, 10, 18 & 26  or  5, 18, 51, 44 etc.

ie. each port must be from a different port group.

Jon

[raulzulueta]

I am using port-channel for throughput as well. As I understand form your post, if I want to

use 4 ports on the line card I will use for example port 1,9,17 and 25 to group 4 ports

into a port-channel, right?

Thanks.

[Jon Marshall · Accepted solution]

raulzulueta wrote:
I am using port-channel for throughput as well. As I understand form your post, if I want to
 use 4 ports on the line card I will use for example port 1,9,17 and 25 to group 4 ports
 into a port-channel, right?
Thanks.

Yes, that's correct.

Jon

[glen.grant · Accepted solution]

Or split the ports across different cards .  Some cards have the oversubscription issue so you can't group ports together like 1-4 .