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DHCP client fails to get IP address (Modem EM7430) [Resolved]

O/S: Raspberry Pi running Raspbian GNU/Linux 8 (jessie)

Kernel: Linux 4.9.24-v7+

Ran ip addr and confirmed wwan0 and wwan1 interfaces are created.

wwan0:  mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
link/ether ce:d3:4d:fc:a7:9b brd ff:ff:ff:ff:ff:ff
inet brd scope global wwan0
    valid_lft forever preferred_lft forever

wwan1: .....

Successfully started

qmi-network /dev/cdc-wdm0 start


qmicli -d /dev/cdc-wdm0 --wda-get-data-format

and got result

                        QoS flow header: no
                    Link layer protocol: 'raw-ip'
       Uplink data aggregation protocol: 'disabled'
     Downlink data aggregation protocol: 'disabled'
                          NDP signature: '0'
Downlink data aggregation max datagrams: '0'
     Downlink data aggregation max size: '0'


qmicli -d /dev/cdc-wdm0 --nas-get-signal-strength

and got result

     Network 'umts': '-103 dBm'
     Network 'umts': '-103 dBm'
     Network 'umts': -10.0 dBm'
IO: '-106 dBm'
SINR: (8) '9.0 dB'


dhclient -v wwan0

and got result

Internet Systems Consortium DHCP Client 4.3.1

Listening on LPF/wwan0/ce:d3:4d:fc:a7:9b
Sending on   LPF/wwan0/ce:d3:4d:fc:a7:9b
Sending on   Socket/fallback
DHCPDISCOVER on wwan0 to port 67 interval 4
DHCPDISCOVER on wwan0 to port 67 interval 8

I tried a lot of times and still cannot get the IP address.

Any help is appreciated.


Also, I have tried to change the link layer protocol to 802-3

qmicli -d /dev/cdc-wdm0 --wda-set-data-format=802-3

The message said 'Successfully set data format', but the link layer protocol still is 'raw-ip'.

Question Credit: aobs
Question Reference
Asked October 15, 2017
Posted Under: Unix Linux
2 Answers

Thanks all for your help.

I found out that the EM7430 does not support 802-3 and is raw ip only. It does not work with dhclient nor dhcpcd.

credit: aobs
Answered October 15, 2017

Couldn't the problem be with the server? Did you try other devices/PCs to make sure they are getting an IP or not? The problem could possibly be with the DHCP server for some reason. Make also sure you are not using a static IP configured on the interface. (I can see you are getting an APIPA address but what is the config in the wwan0.conf for example?

credit: Amjad Abdullah
Answered October 15, 2017
I can use dhcp to get IP address for my eth0 device. So, it is working fine. I suspect the EM7430 is raw-ip only and dhcp will not work. I need to confirm this. – aobs Oct 11 at 8:31
 CanDoerz  1 month ago
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