WS-X6748-GE-TX over-subscription ? line rate ? please help !

[Shlomy Maron]

WS-X6816-10GE over-subscription ? line rate ? please help ! | LAN, Switching and Routing | Cisco Support Community | 6016 | 12914101

Hi,

I didn't understand the documentation - what is the throughput of WS-X6748-GE-TX with CFC sub module ?

what would I gain if I buy DFC sub module ?

what is the effect of the Port-Grouping ? what are the Port-Grouping ?

I have the following Issue - ports 22 to 30 are in use , while most of them are in 50-70% usage of bandwidth.

one of them complained about packet loss when receiving multicast stream.

the way I've solved it was to move his port to 40, while 30-48 are empty.

I've tested it several times with the same cable - and it is the right solution.

(the multicast stream is incoming from another line card)

so I must ask - isn't WS-X6748-GE-TX line rate module ?

please help with some explanation 

[Philip D'Ath]

I don't know the answer, but multicast (and broadcast) are a little special, since they require duplication of the packet.  It is not as simple as simply forwarding a unicast packet.

[Jon Marshall · Accepted solution]

It's not line rate but it is close.

Whether you have a sup720 or a sup2T that module has 2 x 20Gbps to the switch fabric and the port groupings are 1 - 24 get 20Gbps and 25 - 48 get 20Gbps.

So it is oversubscribed in that in theory you can have 48Gbps from connected devices in and only 40Gbps to the switch fabric but it is unlikely you will have all 48 ports transmitting simultaneously.

You may well have solved the issue by moving it to one of the port groups that was not so heavily in use.

Using a DFC would increase the throughput of the module in that it could make forwarding decisions locally but it still only has 40Gbps combined to the switch fabric and that does not change.

Jon