How? My modem is already in “stick mode”.

[EDIT]

Googling …

https://forum.openwrt.org/t/direct-network-mode-for-hilink-e3276-4g-stick/11399/4

… I found this configuration is partially (*) working

config interface 'modem_1_1'
	option ifname 'wwan0'
	option mode 'umts'
	option apn 'iliad'
	option proto 'ncm'
	option device '/dev/cdc-wdm0'
	option dialnumber '*99#'
	option metric '40'
	option disabled '0'

I edited /etc/config/network manually and restarted the network with the command

service network reload

(*) only if the modem is connected to router before the boot.

Any hint?

Another issue: sometime using the above the router is connected to Internet, host connected to router not.

Some output of the router

ifconfig

br-lan    Link encap:Ethernet  HWaddr 94:83:C4:05:23:6B  
          inet addr:192.168.8.1  Bcast:192.168.8.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:6121 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6268 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:597436 (583.4 KiB)  TX bytes:4338150 (4.1 MiB)

          ...

wwan0     Link encap:Ethernet  HWaddr 0C:5B:8F:27:9A:64  
          inet addr:10.152.27.181  Bcast:10.152.27.183  Mask:255.255.255.252
          inet6 addr: fe80::e5b:8fff:fe27:9a64/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:298 errors:0 dropped:0 overruns:0 frame:0
          TX packets:499 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:27487 (26.8 KiB)  TX bytes:39439 (38.5 KiB)

route -n

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.152.27.182   0.0.0.0         UG    40     0        0 wwan0
10.152.27.180   0.0.0.0         255.255.255.252 U     40     0        0 wwan0
192.168.8.0     0.0.0.0         255.255.255.0   U     0      0        0 br-lan

ping -c 4 8.8.8.8

PING 8.8.8.8 (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: seq=0 ttl=114 time=460.507 ms
64 bytes from 8.8.8.8: seq=1 ttl=114 time=1260.782 ms
64 bytes from 8.8.8.8: seq=2 ttl=114 time=940.412 ms
64 bytes from 8.8.8.8: seq=3 ttl=114 time=100.170 ms

--- 8.8.8.8 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 100.170/690.467/1260.782 ms

ping -c 4 google.com

PING google.com (216.58.208.174): 56 data bytes
64 bytes from 216.58.208.174: seq=0 ttl=117 time=749.371 ms
64 bytes from 216.58.208.174: seq=1 ttl=117 time=79.237 ms
64 bytes from 216.58.208.174: seq=2 ttl=117 time=108.975 ms
64 bytes from 216.58.208.174: seq=3 ttl=117 time=95.544 ms

--- google.com ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 79.237/258.281/749.371 ms