Wifi connects and has an IP address but no internet when using school network

Question

I have 4 Raspberry Pi3 B+ at my lab and three of them have no issues connecting to the school network.

ifconfig returns:

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 100.91.145.63  netmask 255.255.240.0  broadcast 100.91.159.255
        inet6 fe80::db97:a1f3:e79f:9f7c  prefixlen 64  scopeid 0x20<link>
        inet6 2607:f720:f00:486d:9d25:5646:887d:5078  prefixlen 64  scopeid 0x0<global>
        ether b8:27:eb:e0:70:be  txqueuelen 1000  (Ethernet)
        RX packets 2134272  bytes 295038009 (281.3 MiB)
        RX errors 0  dropped 1355  overruns 0  frame 0
        TX packets 2608193  bytes 3347236932 (3.1 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

But using the same wpa_supplicant.conf, the fourth one has trouble connecting. It takes longer than the other three to get connected, and ifconfig returns different inet and broadcast addresses:

inet 169.254.66.213 netmask 255.255.0.0 broadcast 169.254.255.255

It has no internet connection, and I cannot ping the fourth device from all other devices (they are in the same room).

ping 8.8.8.8 returns Destination Host Unreachable.

arp - returns ? (169.254.66.1) at <incomplete> on wlan0

Additional information:

I double checked wpa_supplicant.conf and there is no spelling issues, and it works on the other three Pis. When I brought it home and switched to home network, it worked fine.

Any help is appreciated.

Answer 1

For some reason you are not getting an IP address for this Pi.

The 169.254 IP range is the Link Local range for IPv4 and normally set if no DHCP server is acknowledging your request for an address.

This could be due to:

• You not connecting to the Wifi
• The network not allowing you an IP address (possible MAC filtering)
• The DHCP server being down
• All IP addresses for the sub-net being allocated
• Addresses being issued manually (big sheet with MAC and IP addresses on them)
• Possible duplicate name of the Pi on the same network / NetBIOS network (though this often just causes issues rather than no address)

By the look at the output of the connected Pi (100.91.145.63) the school does not provide an IPv6 network as that also has a link-local address (fe80:) No idea why they are 'messing around' with such strange IP and sub-net masking as there are plenty of ranges that are publicly available and not looking like 'Shared Address Space' ownership - their choice though...

You need to talk to the network or IT team at school - this is not one we can really help with.