In a HPE C7000 blade system a common method of accessing the network is through Flex Fabric/Flex-10 modules. These modules are not fully featured switches, but still have some switch features built in. Another alternative is to use a real switch such as the HPE 6125XLG or Cisco Nexus B22HP FEX.
A real switch has many technical benefits over a FlexFabric system, but has a different approach for configuration than the FlexFabric (that has server admins as their main target and is often hated by people who know networking). The 6125XLG has a CLI that has a similar feel as IOS, but not as much as NXOS or ProCurve. The 6125XLG is the heritage of a cooperation between 3Com and Huawei that HPE bought a few years back and is often referred to as H3C and the CLI is referred to as Comware. It's a blade integrated switch with 10GbE facing the blade servers and both 10GbE (SFP+) and 40GbE (QSFP+) uplinks that can be used to connect to the network.
One problem I found while trying to configure this switch was the lack of good documentation. There is a lot of documentation available, but a lot of it is for Comware v5 while the 6125 uses Comware v7. The 6125XLG Fundamentals Configuration Guide stated that it was important to use the command line class aux as part of the stacking (IRF) process, but this command was not available on my switches.
It turned out that the firmware that came preinstalled had a bug that prevented you from stacking the two switches without the use of a RS232 cable. The HPE forums had many helpful posts, but posting there didn't provide me any answers from active users. I did however find a couple of blog posts that helped me going even though they didn't really provide a solution.[HP]line class aux ^ % Unrecognized command found at '^' position.
Upgrading the firmware of both switches from Release 2306 to Release 2422P01 before trying to do anything else solved this problem. The firmware upgrade is described at length in the firmware download package. I chose to upload the firmware image to the switches using ftp. I could now stack my switches according to the Fundamentals Guide (and this HPE Support article: HP 6125g Switch Series - How to Configure Intelligent Resilient Framework (IRF).