gen2 hardware / vNIC questions

[NaelShahid_2]

Please could someone assist in answering these question for me, I keep hearing conflicting information:

1 – New VIC cards support 256 vnics, why do I keep seeing 116 vnics? (Is this is an OS limitation)

2 – Is it correct that with the new gen2 hardware (6248, 2204/8, VIC12xx) the number of vnics has no relation to the number of uplinks between the IOM and FEX?

3 – Assuming the 116 number mentioned above is an ESXi maximum can you in theory have 16 x half width blades each with 116 vnics (total 1856) using VMFEX (none high performance) to a single pair of FIs?

[Robert Burns · Accepted solution]

Nael,

1.  The 1240 and 1280 theoretically support 256 vNICs.  There are further limiations by the IOMs, Interconnects and Host OS, BIOS etc which need to be taken into consideration.  The lowest supported value will be your limit.

2. No.  The total # of vNICs does still depend on the # of IOM <-> FI links.  Calculations are below.

Gen 1 VIC:

(15 * x) - 2  where x is the # of acknowledged IOM links. 

Gen 2 VIC:

(63 * x) - 2  where x is the # of acknowledged IOM links. 

The 116 vNIC limit is the likely first limitation you'll see running the 6200/2208 combination of hardware in regards to Dynamic vNICs (VMFEX).  For regular static NICs you'll probably hit the Host OS limit well before that.  ESX has a limit 32 Ethernet NICs.

Full configuration limits are documented here:

http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/configuration_limits/2.0/b_UCS_Configuration_Limits_2_0.pdf

Regards,

Robert

[NaelShahid_2]

Thanks Robert.

Ok, understanding a little better now. With dynamic vnics this does not count towards to 32 Ethernet NIC max with ESX as these are not present on the host. This being the case do you know why 116 is listed as the max with ESX?

My example was maybe a little extreme! It would be more like 6 x static NICs with a max of 60 dynamic NICs per blade.

[Robert Burns]

Dynamic vNICs bypass the hypervisor and would not count towards your OS-presented NIC total.  This is why the Dynamic vNICs scaled beyond what the hypervisor hosts lists as supported.

The amount of Dynamic vNICs that can be assigned to VMs is actually 112.  We reserve 2 additional VIFs for the Static Ethernet Uplinks and 2 for FC vHBAs.

The 116 per adaptor scale limitation of VM-FEX VIFs was decided by our Product teams for the current 2.x version of UCSM software.  This may be increased in future releases.

Regards,

Robert

[NaelShahid_2]

thanks again

regards