Shared Vs. Dedicated port mode in Nexus 7000

I took the example of line card N7K-M132XP-12 to explain the dedicated and shared mode.

Please refer to the below architecture of the line card. I got this from Cisco document.

As you can see there is a 4:1 MUX which combines traffic from four ports and send it to replication engine via one 10Gig link. It means all four ports cannot send individual 10 Gig traffic at the same time. 10 Gig of connectivity is shared between the four ports. It is called oversubscription. As we can notice this card has 4:1 oversubscription.

Which ports will share the BW is dependent on the model of the card. There are cards available which don’t have any oversubscription and hence can send data on the line rate.

As mentioned above port grouping varies from card to card. Here 10Gig of BW is shared as shown below

1, 3, 5, and 7

2, 4, 6 and 8

And so on ….

                                             

                                                     Shared Mode                                           Dedicated Mode     

Shared Mode: It is the default mode where 10Gig of capacitiy is shared by group of ports.

Below is the  command to configure the port in shared mode. Generally we require it when we convert the port from dedicatd to share.

Switch(config)# Interface Eth3/1

Switch(config-if )# rate-mode shared

Dedicated Mode: In this mode, 10Gig of bandwidth can be allocated to one port of the group and rest will be disabled.  Below is the command to allocate the 10Gig of BW dedicated to a port.

Switch(config)# Interface Eth3/1

Switch(config-if )# rate-mode Dedicated