3 replies Latest Post - ‏2013-05-06T17:15:16Z by an_ibm_user
5 Posts

Pinned topic Nic card numering and switch module bay

‏2013-04-19T06:47:58Z |

In the IBM H chassis for example, typically you may use switch module bays 1-4 with internal 1gb nics to the blades. My question is are the switch bays usually mapped statically to the interface card instance number. I know this also may vary on the operating system used, for example - a new installation of rh 6.3 and if all the blade hardware is the same:

Would eth0 be mapped to switch bay1, eth1 mapped to switch bay2 etc.

In Solaris I have always seen the bnx interfaces map the same across blades, cant comment for other o/s's.

Are there any circumstances this changes? for example if the first nic is not functioning could the OS allocate eth1 to switch bay1.

Any experiences of this? (background is we need a script to configure blade interfaces, and need to know if the instance numbers can change).

  • Josh_Corder
    94 Posts

    Re: Nic card numering and switch module bay

    ‏2013-04-22T13:48:54Z  in response to chrisc100

    They are statically defined.  Onboard NICs map to Bay1, CFFh HEA expansion daughter cards on the blades are mapped to module 2 I believe.  At least for sure in the BC-S because there are only two modules.  This is not configurable.  In your example eth0 and eth1 will always be mapped to the switch in bay 1.  It is not OS dependent as it is directly mapped to the chassis midplane.

    • windsurf1970
      5 Posts

      Re: Nic card numering and switch module bay

      ‏2013-04-23T11:43:55Z  in response to Josh_Corder

      eth0 is mapped to switch bay 1 internal port 1, and eth1 is mapped to switch bay 2 internal port 1.

      If you are running windows, you'll have to compare MAC addresses shown in the AMM's Hardware VItal Product Data and that shown in Windows. I've experienced that Windows typically finds the second nic going to bay 2 first and assigns it as eth0.  This can be misleading if your switches are configured differently.

      Updated on 2013-04-23T11:48:13Z at 2013-04-23T11:48:13Z by windsurf1970
  • an_ibm_user
    21 Posts

    Re: Nic card numering and switch module bay

    ‏2013-05-06T17:15:16Z  in response to chrisc100

    In a BladeCenter H chassis, the onboard blade NICs map to IOM1 and IOM2, the CIOv NICs map to IOM3/IOM4, and the CFFh NICs map to IOM7/IOM9 or IOM7/IOM8/IOM9/IOM10 depending on the card type.

    You can do some reading on how the kernel assigns interface names, but basically the interfaces are named as modules are loaded. For example, the onboard NICs get assigned when the bnx2 module is loaded. They don't guarantee that modules will be loaded in the same order, so if you want consistent naming, you should write some udev rules to assign names in a deterministic way. Udev can rename devices from what the kernel assigns at module load time. You could, for example, assign names based on PCI addresses, which are consistent among blades of the same model.

    Many distributions create udev rules (using MAC addresses) the first time a device is seen so that it will get the same name after every boot, but it's not guaranteed to be the same name as another blade with the same hardware.