Why my gateway can't register with backend ?

[ericccccccc]

Describe the bug
I've follow the instructions on the OpenMTC docs to run the gateway & backend on my ubuntu.
But my gateway CAN'T registered to backend.
Does something i miss it ?
thx

###Setup###
[ Backend ]
docker run -ti --name backend -p 0.0.0.0:18000:18000 -e "ONEM2M_CSE_ID=backend" -e "ONEM2M_NOTIFICATION_DISABLED=false" openmtc/backend-amd64 -v

[Gateway]
docker run --name gateway -p 0.0.0.0:8000:8000 -e "EXTERNAL_IP=" -e "ONEM2M_HTTP_TRANSPORT_PORT=8000" -e "ONEM2M_CSE_ID=gw" -e "ONEM2M_REMOTE_CSE_POA=http://localhost:18000" -e "ONEM2M_REMOTE_CSE_ID=backend" -e "ONEM2M_NOTIFICATION_DISABLED=false" -e "ONEM2M_REGISTRATION_DISABLED=false" openmtc/gateway-amd64 -v
docker run openmtc/gateway-amd64

Screenshots
I've confirm that both have running on console
But the gateway console show the register error

[zskevind]

You should run docker with --network="host"(linux only) or change the "poa" configuration of remote_cses into the actual container address, eg. 172.17.0.2