What does `NO-CARRIER` and `DOWN` mean for a wireless interface?
There is no document that would tell you what specially means for wireless. If your wifi is UP
and NO-CARRIER
means that is administratively up(ip link set dev wlan0 up
) but not associated and authenticated with a SSID. Only LOWER_UP
means that link layer is operational.
ip link list wlan0
and iw wlan0 link
are 2 ways to retrieve link status information. The second form will show you if associated with a SSID, and show relevant wireless information.
Probably the cause of your link problems are related with Wireless power saving configurations, and thus the DORMANT
state of your interface.
Netlink interface flags:
IFF_DORMANT - Driver signals dormant
Check out the links below with instructions on how to chance this behavior.
Additional Documentation:
- Power Management on Network Interfaces
- How to Connect WIFI using cli - Take a look at some of the outputs.
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adrian
Updated on November 27, 2022Comments
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adrian 12 months
I have a remote server and I log output of certain commands while the server cannot access the internet.
It uses a wireless interface to connect to the internet.
In a working state the output of
ip link list
shows:3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DORMANT qlen 1000 link/ether 00:13:ef:b0:29:74 brd ff:ff:ff:ff:ff:ff
When it is not working the output of
ip link list
shows:3: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DORMANT qlen 1000 link/ether 00:13:ef:b0:29:74 brd ff:ff:ff:ff:ff:ff
What does this
NO-CARRIER
andDOWN
mean for a wireless interface? In the case of ethernet, this would mean that the cable is disconnected.I would also appreciate any advice as to how I can further debug why the connection was not working. I also do a
wicd-cli -y -l
scan during the outage and it appears that the access point is still broadcasting. I cannot find any other hardware or software errors in the kernel messages.-
Admin almost 9 yearsIt means the same thing as it does for a wired interface: you're disconnected.
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Admin almost 9 years@psusi Is there some documentation that tells that and could you share it please.
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Admin almost 9 yearsI wouldn't think you would need explicit instructions that the meaning you already established for that flag didn't change to something completely different just because you're using a wireless adapter.
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