Switching Capacity & Catalyst 6500

[ijlal.farooqi]

Friends,

Could someone clarify the following statement from Cisco 6500 Supervisory Engine 720 datasheet

-Delivering upto 40Gbps per slot of switching capacity, 720 Gbps aggregate bandwidth.

Like does this mean that a single slot from the 6500 chassis will switch 40Gbps of data. If for instance i have a 16-port 10 Gigabit Ethernet Fiber module, which means a total of 160 Gbps. Then how will the switch manage this data.

Kindly clarify as i am confused of this concept.

Regards

[Jon Marshall · Accepted solution]

It means that each slot is capable of supporting 40Gbps to the switch fabric.. Whether or not the module can support 40Gbps depends on the module eg.

WS-X6548-GE-TX is a 10/100/1000 Mbps linecard. It has only an 8Gbps connection the switch fabric. It doesn't matter that the 6509 can support 40Gbps per slot, this linecard can only use 8Gbps of the available 40Gbps. Note also that this does not mean that the remaining 32Gbps can be used elsewhere. It is fixed per slot. Obviously this linecard is very oversubscribed ie. you can have 48 devices connected at 1Gbps but only 8Gbps to the switch fabric.

WS-X6748-GE-TX is again a 10/100/1000 Mbps linecard. But this linecard can use the full 40Gbps because it has 2 x 20Gbps connections to the switch fabric. Again it could in theory be oversubscribed because you have 48Gbps from clients and only 40Gbps to the switch fabric however it is unlikey that all 48 devices will be transmitting 1Gbps simultaneously so it is unlikey to be oversubscribed in pratice.

The module you ask about ie. the 16 port 10Gbps module still only has 40Gbps to the switch fabric. So yes you can have 160Gbps in  (from connected devices) and only 40Gbps to the switch fabric. So it is quite heavily oversubscribed ie 4:1. If you wanted to ensure each port ran at wirespeed then you can only use 4 of the 16 ports. Note also if you did use just 4 you need to check the port groupings as ports share ASICs.

You may want to look at the Sup2T if you need more throughput. Even with that it increases the slot capacity to 80Gbps so this module is still oversubscribed 2:1

Jon

[Joseph W. Doherty]

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Posting

To add to Jon's post, believe you need a -E chassis to get 80 Gbps per slot.  Also, the sup2t support 80 Gbps on all slots of a 6513-E whereas sup720 only supports 40 Gbps on the bottom most 5 slots, 20 Gbps on the others for 6513s (which restricts usage of some line cards).

When working with high bandwidth capacity line cards, you can bump into forwarding performance issues as the sup720 is rated at 30 Mpps for fabric cards.  Performance capacity is increased by adding DFCs to line cards that support them, which, by default, don't have them.  The 6716 card, the 8x 10 gig card, comes standard with a DFC, but the other 67xx cards do not.