Setting up DHCPD on master PI

This tutorial how to setup DHCPD and NAT so that the slave PI can access the internet through the NAT (ETH0->WLAN0) running on Master PI. This tutorial also describe how to setup the DHCPD to automatically allocated IPs to PI or PCs.

Key Aspects

  • Setup /etc/dhcp/dhcpd.conf.
  • Setup /etc/default/isc-dhcp-server
  • Setup /etc/systcl.conf

Deploy

Also the Kubedge team went through the process, it has not been documented yet. Still some example files are available bellow.

DHCP server

We want to install a DHCP server so that the additional PI obtain a IP address in the 192.168.2.1 when connected through the switch.

sudo apt-get install isc-dhcp-server

Check the setup of the dhcp server

diff /etc/default/isc-dhcp-server /home/pirate/proj/kubedge/kube-rpi/config/cluster1/hypriotos/kubemaster-pi/etc/default/isc-dhcp-server
vi /etc/default/isc-dhcp-server

Update the dhcpd.conf. Comment out the fix allocation at first until you have access to the eth0 mac address.

diff /etc/dhcp/dhcpd.conf /home/pirate/proj/kubedge/kube-rpi/config/cluster1/hypriotos/kubemaster-pi/etc/dhcp/dhcpd.conf
vi /etc/dhcp/dhcpd.conf

sudo service isc-dhcp-server restart
sudo service isc-dhcp-server status

Network Address Translation

Check the ipforwarding setup

diff /etc/sysctl.conf /home/pirate/proj/kubedge/kube-rpi/config/cluster1/hypriotos/kubemaster-pi/etc/sysctl.conf
vi /etc/sysctl.conf

The Master PI acts as a router from eth0 to wlan0 for the other nodes.

sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
sudo iptables -A FORWARD -i wlan0 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i eth0 -o wlan0 -j ACCEPT
sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"

You can go an uncomment the iptable in the eth0

vi /etc/network/interfaces.d/eth0

Reference Files

Verification

This is where is important to have a 5 ports switch for a 3 nodes cluster , and a 8 ports switch for a 5 nodes cluster.

sequenceDiagram participant PC participant MasterPI participant Internet PC->>MasterPI: Get IP MasterPI->>PC: Return IP in 192.168.2.x PC->>MasterPI: eth0 IP traffic loop Linux NAT MasterPI->MasterPI: translate eth0 IP into wlan0 IP end MasterPI->>Internet: wifi IP traffic Internet->>MasterPI: IP traffic MasterPI->>PC: IP traffic

Plug your laptop onto the switch using an ethernet cable. If the master PI is configured properly (dhcpd, network/eth0..), the master PI will acts as a router. It will provide the laptop with an IP address in the 192.168.2.0/255 range.

SSH to the node.

ssh 192.168.2.1 -l pirate

On your PC itself, open a command prompt or cygwin

ipconfig /all

If the previous test is successful, the Name Server list should contain the IP and your home router, and you should be able to surf the internet.

WIP