I recently have had a few people ask me what Cisco UCS adapter placement policies are used for and how/when to use them. This post will hopefully answer those questions and give a few examples.
First I will start with the Cisco definition of what vNIC/vHBA placement policies are. This definition was copied from the Cisco UCS Manager GUI Configuration guide – Cisco UCS GUI Configuration Guide
vNIC/vHBA placement policies are used to assign vNICs or vHBAs to the physical adapters on a server. Each vNIC/vHBA placement policy contains two virtual network interface connections (vCons) that are virtual representations of the physical adapters. When a vNIC/vHBA placement policy is assigned to a service profile, and the service profile is associated to a server, the vCons in the vNIC/vHBA placement policy are assigned to the physical adapters. For servers with only one adapter, both vCons are assigned to the adapter; for servers with two adapters, one vCon is assigned to each adapter.
You can assign vNICs or vHBAs to either of the two vCons, and they are then assigned to the physical adapters based on the vCon assignment during server association. Additionally, vCons use the following selection preference criteria to assign vHBAs and vNICs:
- All
The vCon is used for vNICs or vHBAs assigned to it, vNICs or vHBAs not assigned to either vCon, and dynamic vNICs or vHBAs.
- Assigned-Only
The vCon is reserved for only vNICs or vHBAs assigned to it.
- Exclude-Dynamic
The vCon is not used for dynamic vNICs or vHBAs.
- Exclude-Unassigned
The vCon is not used for vNICs or vHBAs not assigned to the vCon. The vCon is used for dynamic vNICs and vHBAs.
For servers with two adapters, if you do not include a vNIC/vHBA placement policy in a service profile, or you do not configure vCons for a service profile, Cisco UCS equally distributes the vNICs and vHBAs between the two adapters
Usage Scenarios
Half-width Blades (B200-Mx)
If you have half-width blades (B200-Mx) then you will only ever have a single mezzanine card or vCon1. In this case you would only use a vNIC/vHBA placement policy in these two scenarios:
- In a VN-Link in hardware configuration and you are attaching a Dynamic vNIC Connection Policy to the service profile. In this scenario a vNIC/vHBA Placement Policy is required so that the dynamic vNICs get assigned after the non-dynamic vNIC/vHBAs. This guarantees that the ESX vmnics and HBAs are at the top of the PCI numbering and that some of the dynamic vNICs aren’t intermixed. Here is a screen shot of this configuration, anything not assigned (dynamic vNICs) are placed below the assigned vNICs/vHBAs.
- To force the PCI numbering of the NICs/HBAs as seen by the operating system. If you wanted to make sure the HBAs were seen before the NICs or vice versa you could do that with a placement policy.
Full-width Blades (B250-Mx, B440-M1)
- Use a placement policy to evenly distribute vNICs and vHBAs across 2 mezzanine cards (vCon1 and vCon2). Here is a screen shot of this configuration,
- You have two different type of mezzanine cards; Cisco UCS VIC M81KR (aka Palo) and Cisco CNA M71KR (aka Menlo). Lets say for compatibility reasons you want all vNICs on the Palo and all vHBAs on the Menlo. In this scenario would create a placement policy to configure this assignment. Here is a screen shot of this configuration,
- In a VN-Link in hardware configuration and you are attaching a Dynamic vNIC Connection Policy to the service profile and you want all of the Dynamic vNICs to be on one adapter and regular vNICs/vHBAs to be on the other.
- You have two different types of mezzanine cards; Cisco UCS VIC M81KR (aka Palo) and Cisco CNA M71KR (aka Menlo) and you are configuring VN-Link in hardware. Lets say for compatibility reasons you want all vNICs on the Palo and all vHBAs on the Menlo. In this scenario would create a placement policy to configure this assignment. Here is a screen shot of this configuration,
It is important to note that only the Cisco UCS VIC M81KR (aka Palo) allows you to have more than 2 vNICs/vHBAs per adapter and is the only card that allows for VN-Link in hardware where you have up to 54 Dynamic vNICs that are dynamically assigned to VMs that are configured to be part of the UCSM Managed Distributed Virtual Switch. – VN-Link in Cisco UCS
Jeremy Waldrop's Blog 
Thanks Jeremy,
I was having a tough time figuring out these placement policies. Your post made this very easy.
Great, I am glad you found it helpful.
Thanks for clarifying these concepts Jeremy. It’s helpful to see the config with context.
Jeremy- thanks for this post, it really is simple once you get it but I wasn’t putting it together that vcons were the mezz card and the order had to be set there.
Jeremy, Thanks for the time here but if you could clarify for me a little more on the vcon stuff, It would help my sanity level a little especially with us now seeing 4 on a system that only has 2. That said I didnt think much about vcon fuctions until now. Is the vcon1 10G to FabA, vcon2 10G to FabB, or each a 5G so to speak, muxed to 10G and connected to both fabrics ?? In the beginning I didnt question because I had single card, dual fabrics, so vcon for each fabric, done. Now seeing four of them in single card system, AND having vnic’s/vhba’s on 3 and 4 with no errors or complaints got the wheels spinning in my head after reading this. Can you please advise WHAT exactly those virtual representations of those physical adapters are tied to A, B, BOTH ?? Was happy with current knowledge, now confused, and globally adding 2 more in the code didnt change how they function, or add more abilities right ? I just figured we couldnt assign anything to 3 or 4 on B200 with single VIC adapter. Please clarify as my ucs rep just got confused on me 🙂
Thanks,
Dave
Dave, vCons are the physical mezzanine cards. In B200, B230 there can only be 1 vCon. In B250, B440 there could be 2 because there are 2 mezzanine slots.
vCons 3-4 are for C-Series rack mounts where you could have 4 PCIe cards.
Ok, so PHYSICAL Mezz adapter, thanks. That tells me that in this card, B200-M2 being half width, all my customers vnics/vhba’s MUST be on vcon1. So same question, how can they be added to 3,4, and now 2 with this clarification, without errors or warnings when it doesnt exist ? Is there a way to mask this, simply because I am seeing it happening and it took me till now to know that means card 1 basically. It’s not stated obviously anywhere, but I was about to post question to you in 2nd of about 6 places I can find you daily 🙂
Thanks so much for quick response, advise on this when you can, direct if you wish, and I’ll start figuring out how to educate all my customers to quit experimenting with cards that arent there. Is there 4 in the C-Series by the way for dual mezz adapters where available as well as the LAN on MB it still comes with ?? Curious as I dont actually see those much now with b-series taking flight.
UCSM will allow a service profile that is mis-configured to use vCon2 to be associated to a B200 blade without error. I have seen customers do this and not understand why the vNIC didn’t work. I usually create custom vNIC/vHBA templates that have vCons 2-4 deleted.
I have yet to integrate a C-Series with UCSM, all of the C-Series we have done have been stand alone.
agreed and same here. I am looking for a c-series at this time to borrow for one of my installs, I wanted to play with it on UCSM after hours one night to see for myself. Thanks for that information, after seeing last weeks issues due to hba’s needed for SAN boot residing in vcon4 of a b200, I think I’ll make a placement policy as part of my standard install right away. While I used one to take care of this customer, I didnt notice I could delete those, so temptation still lingers. Great stuff !
dave
Realy Helpful
Hey,
Perhaps a behavior change, but now UCS seems to tie all vcon’s to whichever adapters (mez cards) it detects on each blade, not allowing vNIC/vHBAs to be left hanging on vcons that don’t exist (as Jeremy described).
http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/gui/config/guide/2.0/b_UCSM_GUI_Configuration_Guide_2_0_chapter_011100.html#concept_BA2C19D814D442C88C43B6B7A557A86F
Hey, every one.
Does anybody know how bandwidth is distruited between vnics? is it configurable?
After checking Cisco UCS configuration guide 2.0, Each vNIC/vHBA placement policy contains four virtual network interface connections (vCons) that are virtual representations of the physical adapters.