5900 IRF - number of IRF links

[fabbb]

Hello all
I have a question about the number of inter-switch links for IRF.

To build IRF with the 5900AF-48G-4XG-2QSFP+ , I will use sfp+ ports as IRF ports.

‘HP 5920 & 5900 Switch Series – IRF Configuration Guide’ states : “If you use one port in a group for IRF connection, you must also use all the other ports in the group for IRF connection.”

Does it means that, on each chassis :
- all 4 sfp+ must be used, whatever the total useful bandwidth of the switch is
- or we can use only 2 sfp+ ports , providing the actual total traffic of the switch is less than 10G, and that the 2 other sfp+ ports will not be used at all ?

Actually, the actual total traffic of the switch is about 1G, so only 1+1 10G IRP ports would be sufficient on each switch (+1 for link redundancy).
I just need the confirmation it will be technically OK.

Thanks for your adivce !

[bamaskas · Accepted solution]

Assuming just two switches will be in the IRF domain, 2 links  in the group are sufficent to merge the switches.

Are you not able to utilize two 40G DAC cables for the IRF links ?

[parnassus]

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@fabbb wrote: Does it means that, on each chassis :

• all 4 sfp+ must be used, whatever the total useful bandwidth of the switch is
• or we can use only 2 sfp+ ports , providing the actual total traffic of the switch is less than 10G, and that the 2 other sfp+ ports will not be used at all ?

It means that if you start by using one, two or three SFP+ of the four's SFP+ Group as IRF logical Port's physical member(s)...then the three, two or one remaining SFP+ can't be used for other typical purposes (as example for single or aggregated uplinks to Hosts/Switches).

So once you use one of them for IRF - being part of a Group -  all of them are immediately reserved for that (possible) use even if the remaining ones are not bound at all into the specific IRF logical port.

It is a requirement and, also, a restriction: think about it positively as a sort of reservation for future usage (within the IRF scope).

[fabbb]

Hi Bamaskas, thanks for your reply.

"Assuming just two switches will be in the IRF domain" : yes ut is

"Are you not able to utilize two 40G DAC cables for the IRF links ?" : sure, it is also an option. The advantage would be to keep the 4 sftp+ port free for futur need. But I guessed 40G DAC were more expensive than 10G DAC.

"2 links in the group are sufficent to merge the switches." : it is by experience (you set up one IRF this way), or you have some reference ?  (it was my thought also, but haven't seen that written in HPE doc, and I need to be sure before ordering)

[fabbb]

Thanks Parnassus, it confirms my thought and Bamaskas answer !

[pombeii]

@fabbb and @parnassus

Hi,  will the description be clearer if it is changed to the following:

If you use physical interfaces that are grouped in hardware for IRF connection, follow these restrictions and guidelines:

• If you use one physical interface in a group as an IRF physical interface, the remaining physical interfaces in the group can only act as IRF physical interfaces. You cannot use them for any other purposes. To use all physical interfaces in a group for any purpose other than IRF physical interfaces, do not bind any of the interfaces to an IRF port.
• You must shut down all physical interfaces in a group before you can assign or remove any of the interfaces to or from an IRF port. To bring up the interfaces after the assignment or removal is complete, execute the undo shutdown.

Thanks!

Pombeii

[parnassus]

Yes, definitely. That's the way on some IRF Configuration Guides this requirement/restriction is described yet, if I recall correctly.