I was not able to find doc against the abover module, but found under config guide for 15.1SY that recommendation is to put them in performance mode as below for VSL links
Note • When using the ports on a switching module that can operate in oversubscribed mode as VSL links, you must operate the ports in performance mode, not in oversubscription mode. Enter the no hw-module switch x slot y oversubscription port-group num command when configuring the switching module. If you enter the no hw-module switch switch_number slot slot_number oversubscription command to configure non-oversubscription mode (performance mode), then only ports 1, 5, 9, and 13 are configurable; the other ports on the module are disabled.
AAAnd for 6880 I see the below as 2:1 oversubcribed
Ovversubsription 16P 10G at 2:1 in oversubscription mode (default) for base module and port cards 8P 10G at 1:1 in performance mode (configurable) for base module and port cards
Hope this helps.
thanks for the reply.
That's the same doc I found but it's not clear to me: I need to deploy a couple of 6880 in VSS and I need to understand how may free ports I'll have after the VSL configuration in order to put in the 6880 the right number of 16P linecards.
The problem with the above doc is that it is referring to a generic line card and not to this particular one :(
If I understand weel, when I put this card in performance mode it means that I'll be able to use only 8 ports; isn't it ?
Yes Luciano, you are right, you will be able to use only 8 if you enble performace mode for whole module.
But i think can you check whether you can configure only for specific port-groups. Looking the below, you can configure port-group depending on your need and allowing the other ports on different port-groups continue to work in over subscription mode. In that way you may reduce port-wastage. Hope this helps and kindly remeber to rate all useful posts.
I went trough a lot of BRK documents, but I was unable to find the answer too :(
BRKARC-3465, BRKCRS-2468, BRKCRS-3035, BRKRST-8645 and LTRCRS-2002
... it's a little bit weird ... :-|
I think the answer is in the post Madhu made ie. -
When using the ports on a switching module that can operate in oversubscribed mode as VSL links, you must operate the ports in performance mode
There is no ambiguity in that statement ie, it's not a recommendation it is saying you must do that.
This applies to any module you use, it doesn't have to mention your specific module which is why you cannot find any document specifically mentioning your module.
However it also says you don't necessarily need to run all ports on the module without oversubscription.
So you can run the VSL ports in performance mode ie. no oversubscription without actually having to enable performance mode for whole module.
thanks for your update.
It's seems weird to me because the document states for sure that you must operate in performance mode but also states that you can use port groups.
This, regarding the C6880-X-16P10G module, is not really true:
"Supports a “performance mode” configuration that will disable the second half (eight) of the ports, per the Port ASIC, and enable 1:1 throughput."
This is due to the fact that, according to the HW specification of the module, you have 8 ports on each ASIC.
I agree the wording is a bIt misleading.
When it says you must operate in performance mode, as I read it, it means the ports used for the VSL must be in performance mode.
But it doesn't mean all ports must be in performance mode.
What normally happens on a module like this is that 8 ports are grouped together and get 40Gbps to the switch fabric via the port ASIC and the other 8 ports also get 40Gbps.
So you could make sure that for the VSL ports you never had more than 4 ports in that group so they could not be oversubscribed and in the other group you could use all 8 ports at a 2:1 oversubscription.
You just need to know the port groups and that is normally in the release notes but it isn't for this module.
It does say it's based on the WS-6904-40G so perhaps it uses the same port groupings as that.
Perhaps Cisco have an internal document that could clarify.
We are running 6880 with VSL links in oversubscription mode and all seems fine.
I have asked our Cisco SE and his answer was to monitor utilization and if need be change to performance mode.
Not a great answer, but we don't have enough port capacity to allow performance mode at this stage.
Documentation about this product is not very good...hope it changes soon.
6880x#show hw-module switch 1 slot 1 port-group-mapping
1 1, 2, 3, 4, 5, 6, 7, 8,
2 9, 10, 11, 12, 13, 14, 15, 16,
So you can switch port-group 1 to performance mode while leaving port-group 2 in oversubscription mode. The result is:
1,2,3,4 performance mode ports (for one or more VSL ports)
5,6,7,8 disabled ports
9, 10, 11, 12, 13, 14, 15, 16 oversubscribed ports
I agree with Peter.
In our case we could not spare to disable 4 ports so we sit with a situation where we have VSL links in oversubscription mode....
We have had numerous other issues but none thusfar related to VSL being unstable because of this.