This issue is present until branch 6.0.x. The master branch is not affected.

Steps to reproduce:

1. Start Karaf:

   feature:install odl-restconf-all odl-netconf-topology
   

2. Drop ports for test devices:

   sudo iptables -I INPUT -p tcp --dport 17840 -j DROP
   sudo iptables -I INPUT -p tcp --dport 17841 -j DROP
   sudo iptables -I INPUT -p tcp --dport 17842 -j DROP
   sudo iptables -I INPUT -p tcp --dport 17843 -j DROP
   sudo iptables -I INPUT -p tcp --dport 17844 -j DROP
   sudo iptables -I INPUT -p tcp --dport 17845 -j DROP
   sudo iptables -I INPUT -p tcp --dport 17846 -j DROP
   

1. Start 20 devices

   java -jar netconf-testtool-6.0.6-SNAPSHOT-executable.jar --device-count 20 --ssh true --md-sal true --controller-ip 127.0.0.1 --controller-port 8181
   

1. Get all devices

   curl 'http://192.168.56.100:8181/rests/data/network-topology:network-topology/topology=topology-netconf' \
   --header 'Authorization: Basic YWRtaW46YWRtaW4='
   

In all devices, there is at least one device that is not immediately connected, and its ports were not set to drop all packets. These devices connect after some time.