listing parent interface of a vlan
I didn't find a way without any parsing to get the underlying interface, so I give 4 (sometimes just slightly) different ways to get this information, I hope one will be handy.
There's a symlink having the name of the physical interface:
$ ls -l /sys/class/net/vlan2
[...]
lrwxrwxrwx. 1 root root 0 nov. 10 02:12 lower_eth1 -> ../eth1
[...]
-rw-r--r--. 1 root root 4096 nov. 10 01:49 uevent
Method 1
$ echo $(basename $(readlink /sys/class/net/vlan2/lower_*))
eth1
There's uevent
that is handy too:
$ cat /sys/class/net/vlan2/uevent
DEVTYPE=vlan
INTERFACE=vlan2
IFINDEX=24
$ cat /sys/class/net/vlan2/lower_*/uevent
INTERFACE=eth1
IFINDEX=22
Method 2
$ cat /sys/class/net/vlan2/lower_*/uevent|sed -n 's/^INTERFACE=//p'
eth1
As root, there are entries in /proc/net/vlan
:
# ls /proc/net/vlan/
config vlan1 vlan2 vlan3 vlan4 vlan5
# cat /proc/net/vlan/config
VLAN Dev name | VLAN ID
Name-Type: VLAN_NAME_TYPE_RAW_PLUS_VID_NO_PAD
vlan1 | 1 | eth1
vlan3 | 3 | eth1
vlan4 | 4 | eth1
vlan2 | 2 | eth1
vlan5 | 5 | eth2
# cat /proc/net/vlan/vlan2
[...]
Device: eth1
[...]
Method 3
# awk -F ' *\\| *' '$1 == "vlan2" { print $3 }' /proc/net/vlan/config
eth1
Method 4
# sed -n 's/^Device: //p' /proc/net/vlan/vlan2
eth1
Note that in /sys the other direction is also possible with upper_*
:
$ ls -l /sys/class/net/eth1
[...]
-rw-r--r--. 1 root root 4096 nov. 10 01:46 uevent
lrwxrwxrwx. 1 root root 0 nov. 10 02:23 upper_vlan1 -> ../vlan1
lrwxrwxrwx. 1 root root 0 nov. 10 02:18 upper_vlan2 -> ../vlan2
lrwxrwxrwx. 1 root root 0 nov. 10 02:23 upper_vlan3 -> ../vlan3
lrwxrwxrwx. 1 root root 0 nov. 10 02:23 upper_vlan4 -> ../vlan4
$ sed -n 's/^INTERFACE=//p' /sys/class/net/eth1/upper_*/uevent
vlan1
vlan2
vlan3
vlan4
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Rahul
Updated on September 18, 2022Comments
-
Rahul over 1 year
I have a setup with a bunch of vlan interfaces on a physical interface.
Physical interface: eth1 VLANS on top of this: vlan1, vlan2, vlan3
Now, I want to know which is the parent interface of my vlan (for example, here eth1 is the parent interface of these vlans).
I can get this information by running "ip addr show vlan-name" and then in output, I will get vlan1@eth1, but I need to parse the output of this command or by looking at my network config file, parsing it and interpreting it.
Is there another way by which I can get this information without any parsing logic? For example, for bonded interfaces, the information is present in /sys/class/net/ directory and one can simply read files there.
# cat /sys/class/net/bond0/bonding/slaves eth0 eth1
Is there a similar path/file available for vlan tagged interfaces? I couldn't figure out if there is some file I can just read without any parsing and extract this information or any command/utility that just gives the parent interface name.
Kindly do let me know if there are other alternatives to this.
Thanks.
-
A.B about 4 yearsWell OP already had the best method: the
ip
command. When using the newer JSON output andjq
this gives:ip -json link show vlan1 | jq -r '.[]|.link'
=>eth1
. orip -json link show type vlan | jq -j '.[]|(.ifname,"∈",.link,"\n")'
to display all. This should be more reliable