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My Android phone is trying to get DHCP address through WiFi connection, but fails.

Obviously, I might have messed up something in my settings because I couldn't find a complete guide which would let me do everything in one go, thus I had to combine multiple guides, but I still feel a bit new to network configuration on Linux.

What I want to achieve:

- create a WiFi access point and DHCP server where all devices receive IP adresses in the same network. Internet access not required, so no routing needed - just a local network where my server acts as a switch (bridge) providing IP adresses for all devices connected to it through WiFi or Ethernet.

Here's what I have:

  • a Linux machine (actually, Raspberry Pi with Raspbian) with Ralink RT5370 WiFi dongle (which claims to support Access Point) and two Ethernet ports - one is RPi's built-in port and the other is Trendnet TU2-ET100 (chip AX88772)

  • I have installed bridge-utils and dnsmasq and everything works fine with Ethernet connections - all devices connected to RPi Ethernet ports receive their IP addresses from RPi through dnsmasq

  • I have installed hostapd and configured it to be open AP, for starters. I tried to use WPA, but on my Android phone that also failed with "Authentication failure", so I disabled auth. And now my Android device gets stuck while acquiring IP address and then fails.

Here are my config files:

/etc/default/hostapd:

interface=wlan0
hw_mode=g
bridge=br0
channel=1
ssid=FakeTestServer_AP
auth_algs=1
wmm_enabled=0

/etc/default/hostapd:

DAEMON_CONF="/etc/hostapd/hostapd.conf"

/etc/network/interfaces:

auto lo

iface lo inet loopback

auto br0
iface eth0 inet manual
iface eth1 inet manual

iface br0 inet static
        bridge_ports eth0 eth1 wlan0
        bridge_stp off
        bridge_fd 0
        bridge_waitport 0
        bridge_maxwait 0
        address 10.0.0.1
        netmask 255.255.255.0

/etc/dnsmasq.conf:

interface=br0
dhcp-range=10.0.0.2,10.0.0.254,255.255.255.0,12h

Here is what ifconfig shows:

br0       Link encap:Ethernet  HWaddr 00:14:d1:da:c7:dc
          inet addr:10.0.0.1  Bcast:10.0.0.255  Mask:255.255.255.0
          inet6 addr: fe80::214:d1ff:feda:c7dc/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1343 errors:0 dropped:0 overruns:0 frame:0
          TX packets:212 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:83674 (81.7 KiB)  TX bytes:16750 (16.3 KiB)

eth0      Link encap:Ethernet  HWaddr b8:27:eb:74:1f:8c
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:5824 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2800 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1448587 (1.3 MiB)  TX bytes:1057796 (1.0 MiB)

eth1      Link encap:Ethernet  HWaddr 00:14:d1:da:c7:dc
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5353 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1145578 (1.0 MiB)  TX bytes:414153 (404.4 KiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:52 errors:0 dropped:0 overruns:0 frame:0
          TX packets:52 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:3744 (3.6 KiB)  TX bytes:3744 (3.6 KiB)

mon.wlan0 Link encap:UNSPEC  HWaddr 00-C1-40-95-0D-43-00-00-00-00-00-00-00-00-00-00
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7417 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2107086 (2.0 MiB)  TX bytes:0 (0.0 B)

wlan0     Link encap:Ethernet  HWaddr 00:c1:40:95:0d:43
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:182 errors:0 dropped:0 overruns:0 frame:0
          TX packets:122 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:31498 (30.7 KiB)  TX bytes:21682 (21.1 KiB)

To make it clear, I repeat - the bridge and both Ethernet connections work fine, and there are no any errors when I run:

sudo service hostapd restart
sudo service dnsmasq restart
sudo service networking restart

At the very beginning bridge-utils failed with a message

can't add wlan0 to bridge br0: Operation not supported

but after I added bridge=br0 to hostapd settings, bridge-utils did not complain anymore, so I guess, wlan0 got added to the bridge but I'm not sure what's going on there.

How do I get my WiFi working in Access Point mode and be part of the same bridge as both eth0 and eth1 are?

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1 Answer 1

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Looking at your /etc/network/interfaces, I don't see wlan0 as one of the interfaces included in the bridge. Adding that would be the place to start.

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  • Isn't it, though, with bridge_ports eth0 eth1 wlan0 ? And there's an explicit error in that direction: can't add wlan0 to bridge br0: Operation not supported ...
    – Jeff Schaller ♦
    Apr 28, 2019 at 0:16
  • @JeffSchaller Yes, and it's confusing that the error message disappeared when I added bridge=br0 for hostapd, creating impression that wlan0 got bridged together with eth0 and eth1, although it still didn't actually work. So I thought that maybe there are additional steps or different syntax required to make wlan0 bridged.
    – JustAMartin
    Apr 29, 2019 at 8:15

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