[SOLVED] Interface naming

lazydog · 04-15-2015, 09:16 AM

Antoher thread got me thinking and I am trying to figure out the following;

My network interface is enp0s25

The output of lspci is;

Code:

[root@bipanms01 rjs]# lspci
00:00.0 Host bridge: Intel Corporation 4 Series Chipset DRAM Controller (rev 03)
00:02.0 VGA compatible controller: Intel Corporation 4 Series Chipset Integrated Graphics Controller (rev 03)
00:02.1 Display controller: Intel Corporation 4 Series Chipset Integrated Graphics Controller (rev 03)
00:03.0 Communication controller: Intel Corporation 4 Series Chipset HECI Controller (rev 03)
00:03.2 IDE interface: Intel Corporation 4 Series Chipset PT IDER Controller (rev 03)
00:03.3 Serial controller: Intel Corporation 4 Series Chipset Serial KT Controller (rev 03)
00:19.0 Ethernet controller: Intel Corporation 82567LM-3 Gigabit Network Connection (rev 02)
00:1a.0 USB controller: Intel Corporation 82801JD/DO (ICH10 Family) USB UHCI Controller #4 (rev 02)
00:1a.1 USB controller: Intel Corporation 82801JD/DO (ICH10 Family) USB UHCI Controller #5 (rev 02)
00:1a.2 USB controller: Intel Corporation 82801JD/DO (ICH10 Family) USB UHCI Controller #6 (rev 02)
00:1a.7 USB controller: Intel Corporation 82801JD/DO (ICH10 Family) USB2 EHCI Controller #2 (rev 02)
00:1b.0 Audio device: Intel Corporation 82801JD/DO (ICH10 Family) HD Audio Controller (rev 02)
00:1c.0 PCI bridge: Intel Corporation 82801JD/DO (ICH10 Family) PCI Express Port 1 (rev 02)
00:1c.1 PCI bridge: Intel Corporation 82801JD/DO (ICH10 Family) PCI Express Port 2 (rev 02)
00:1d.0 USB controller: Intel Corporation 82801JD/DO (ICH10 Family) USB UHCI Controller #1 (rev 02)
00:1d.1 USB controller: Intel Corporation 82801JD/DO (ICH10 Family) USB UHCI Controller #2 (rev 02)
00:1d.2 USB controller: Intel Corporation 82801JD/DO (ICH10 Family) USB UHCI Controller #3 (rev 02)
00:1d.7 USB controller: Intel Corporation 82801JD/DO (ICH10 Family) USB2 EHCI Controller #1 (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev a2)
00:1f.0 ISA bridge: Intel Corporation 82801JD (ICH10D) LPC Interface Controller (rev 02)
00:1f.2 SATA controller: Intel Corporation 82801JD/DO (ICH10 Family) SATA AHCI Controller (rev 02)

The output of biosdevname -d;

Code:

[root@bipanms01 ~]# biosdevname -d
BIOS device: em1
Kernel name: enp0s25
Permanent MAC: 78:AC:C0:B2:D1:09
Assigned MAC : 78:AC:C0:B2:D1:09
ifIndex: 2
Driver: e1000e
Driver version: 2.3.2-k
Firmware version: 0.5-3
Bus Info: 0000:00:19.0
PCI name      : 0000:00:19.0
PCI Slot      : embedded
Embedded Index: 1

How is my interface being defined?

I am just trying to understand how this all works and how the decisions are made as to the interface name.

Thank you for your time.

Head_on_a_Stick · 04-15-2015, 09:17 AM

Quote:

Originally Posted by lazydog

How is my interface being defined?

http://www.freedesktop.org/wiki/Soft...nterfaceNames/

lazydog · 04-15-2015, 10:39 AM

Thanks for the reply Head_on_a_Stick.

I am still not understanding how we get from

Code:

00:19.0 Ethernet controller: Intel Corporation 82567LM-3 Gigabit Network Connection (rev 02)

to

Code:

enp0s25

fatmac · 04-15-2015, 01:30 PM

Kernel name: enp0s25 => this is what it is as far as the kernel is concerned.
Driver: e1000e => this is the driver the kernel loads so you can use it.
As for why it is called enp0s25, someone in the kernel dev team may be able to say why that is its designated name.

Head_on_a_Stick · 04-15-2015, 02:13 PM

Quote:

Originally Posted by fatmac

As for why it is called enp0s25

...the name tells you where on the PCI bus the device is located and ensures consistent interface naming between reboots and when hardware is changed.

See my link above.

robertjinx · 04-15-2015, 02:42 PM

Code:

 *
 * Two character prefixes based on the type of interface:
 *   en -- ethernet
 *   sl -- serial line IP (slip)
 *   wl -- wlan
 *   ww -- wwan
 *
 * Type of names:
 *   b<number>                             -- BCMA bus core number
 *   ccw<name>                             -- CCW bus group name
 *   o<index>[d<dev_port>]                 -- on-board device index number
 *   s<slot>[f<function>][d<dev_port>]     -- hotplug slot index number
 *   x<MAC>                                -- MAC address
 *   [P<domain>]p<bus>s<slot>[f<function>][d<dev_port>]
 *                                         -- PCI geographical location
 *   [P<domain>]p<bus>s<slot>[f<function>][u<port>][..][c<config>][i<interface>]
 *                                         -- USB port number chain

ethernet = en
bus 0 = p0
slot 25 = s25
is enp0s25

This is done by net_id (udevadm builtin: udevadm test-builtin net_id /sys/class/net/enp0s25) and you can disable it by using net.ifnames=0 at boot time.

robertjinx · 04-15-2015, 02:46 PM

BTW, slot 25 actually equals to slot 19, but 19 is hexadecimal, 25 is decimal, so 19 = 25.

lazydog · 04-16-2015, 01:57 PM

Quote:

Originally Posted by robertjinx

BTW, slot 25 actually equals to slot 19, but 19 is hexadecimal, 25 is decimal, so 19 = 25.

This explains what I was seeing and not understanding. thank you.

And thank everyone else also who replied.