Interface with 14 characters and more fails


In LuCI, attempt to create a new interface with creation of firewall zone with a name of 14 characters and more will fail.

FYI, I didn’t try with 13, but it works with 12 characters.

I guess this is a bug and it should be reported.

It should work with 15 if there’s not another limitation. So not working with 14 is indeed weird.

It’s not a historical limitation of the length of the DOS file name ?

What type of interface are you creating? For some interfaces limit can be under 15 …

The Linux kernel limits the physical interface name length to 15 characters including the automatically added prefix that is added for some protocols (e.g.6in4, pppoa-, pppoe-, gre4t-) or with bridges (br-).

Depending on the protocol type, the logical interface name may thus be limited to only 9 characters. E.g. ‘abcde67890’ is a valid interface name for a normal interface using dhcp, but not for a pppoe interface where the final name would be ‘pppoe-abcde67890’, which is >15 chars.

If using .VLAN notation, an additional 5 characters may be needed, limiting the “parent” interface name to 4 characters for protocols such as GRE. abcd.NNNNgre4t-abcd.NNNN for 15 characters.

Using a too long name will lead to silent errors, with interface creation or modification not being sucessful.

Source: [OpenWrt Wiki] Network basics