What is AlternativeNamesPolicy in Interface naming scheme?

Resolution

The feature AlternativeNamesPolicy is added from RHEL 8.5 and above version where it allow the feature to create alternate names for existing interfaces. It is space-separated list of policies by which the interface's alternative names should be set. Each of the policies may fail, and all successful policies are used. The available policies are "database", "onboard", "slot", "path", and "mac". If the kernel does not support the alternative names, then this setting will be ignored.

      "database"
           The name is set based on entries in the udev's Hardware
           Database with the key "ID_NET_NAME_FROM_DATABASE".

      "onboard"
           The name is set based on information given by the firmware for
           on-board devices, as exported by the udev property
           "ID_NET_NAME_ONBOARD". See systemd.net-naming-scheme(7).

       "slot"
           The name is set based on information given by the firmware for
           hot-plug devices, as exported by the udev property
           "ID_NET_NAME_SLOT". See systemd.net-naming-scheme(7).

      "path"
           The name is set based on the device's physical location, as
           exported by the udev property "ID_NET_NAME_PATH". See
           systemd.net-naming-scheme(7).

       "mac"
           The name is set based on the device's persistent MAC address,
           as exported by the udev property "ID_NET_NAME_MAC". See
           systemd.net-naming-scheme(7).

The goal of introducing the alternate names are:

1. Overcome the IFNAMSIZE limitation.
2. To allow interfaces with multiple names at the same time (multiple udev patterns).
3. To allow use of alternative names as handle for commands.

Note: when you use net.ifnames=0 in kernel options, altname will appear by default in ip addr command.

# ip addr
:
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:33:f8:ae brd ff:ff:ff:ff:ff:ff
    altname enp1s0
    inet 192.168.122.9/24 brd 192.168.122.255 scope global dynamic noprefixroute eth0
       valid_lft 3591sec preferred_lft 3591sec
:

net.ifnames=0 is not recommended. Please see https://access.redhat.com/solutions/2435891

In which version of kernel and iproute can we use altname?

altname is supported in RHEL8.5(4.18.0-348.el8.x86_64). however ip command could not show altname because there was a bug in iproute of RHEL8.5 or less.
You can see altname in the following combination:

  kernel:  4.18.0-348.el8.x86_64 or later
  iproute: 5.9.0-4.el8 or later

How to set up your unique altname temporarily by ip command ?

Note: altname set by ip command will go off after the reboot

# ip link property add dev enp1s0 altname **your_altname**

How to set up your original altname permanently ?

Note: At the moment, the following setup works well in RHEL9 only. (You will be able to use altname in the case of using bond. )

Caution: Please note that the use of OriginalName= is not always recommended. This is because the name of the interface may differ from the name originally recognized by the kernel. Therefore, please test this in your environment before use.

1. create /etc/systemd/network/00my.link

    [Match]
    OriginalName=enp1s0
   
    [Link]
    AlternativeNamesPolicy=
    AlternativeName=myaltname
   

2. reboot

    # reboot
   

3. Check the altname you set up

    # ip a
   

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