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New Member

backplane speed on MDS 9509 director

in our environment we have a fully populated 9509 with 2 supervisors

the chassis we have a mix of 9032 (2Gb), 9148(4Gb), 9016(2Gb),9124(4Gb) line cards

would the backplane speed between line cards be limited to the lowest link speed?

i.e. going from the 9032 to the 9148 would be 2Gbps

Thank you

5 REPLIES
Cisco Employee

Re: backplane speed on MDS 9509 director

Not it will not. You can have a mix of different speed line cards in the same chassis.

New Member

Re: backplane speed on MDS 9509 director

please elaborate on your response

thanks

Cisco Employee

Re: backplane speed on MDS 9509 director

Hi Jie,

Prashanth is right, both linecards will operate at the speed indicated. Beware that the linecards will have some oversubscription (meaning that not all ports in a port group will be able to use their max speed at the same time)

New Member

Re: backplane speed on MDS 9509 director

Thanks for the response but I'm still not clear on the answer

I do understand that there will be oversubscription on the 48 & 24 ports if they're to operate at 4Gbps

when you say both cards will operate at the speed indicated, is that 2Gbps or 4Gbps?

don't the linecard communicate via the crossbar module?

Cisco Employee

Re: backplane speed on MDS 9509 director

Hi Jie,

Any given port will communicate with any other given port on the same switch at the maximum speed that _both_ can attain. A 2Gb port will not magically start working at 4Gb just because it's sending data to a device attached to a 4Gb port. 

This holds true for as long as the link between the linecard and the crossbar is not saturated. This is what oversubscription in this case means: for a 4:1 oversubscription only a quarter of the ports can communicate with the backend at their maximum speed.  While this is oversimplified, it's a good general rule of thumb.

As for your particular case:  the backend of the switch will not force your 4Gb linecards to become 2Gb because there are earlier generation linecards present. You will however not be able to run all of your 4Gb port at an actual sustained data rate of 4Gb at the same time, but this is by design.

I hope this made things clearer for you

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