Access Diskstation from Raspberry Pi (or How to set up dhcpd on raspi eth)

setup_dhcp_instructions

Raspberry Pi has wlan (wireless) and eth0 (ethernet) network interfaces
The following will set 10.0.0.1 IP to eth0
The diskstation should typically get assigned 10.0.0.10 from dhcp

# assign a static address to eth0
sudo vim /etc/dhcpcd.conf
interface eth0
static ip_address=10.0.0.1/24

# now that we have our static IP address set up, we can install and configure a DHCP server
sudo apt-get install isc-dhcp-server
sudo service isc-dhcp-server stop
sudo vi /etc/default/isc-dhcp-server
# edit the INTERFACES environment variable so that the DHCP server only listens on the wired interface
INTERFACESv4="eth0"

# start isc-dhcp-server on boot
sudo cp /run/systemd/generator.late/isc-dhcp-server.service /etc/systemd/system
sudo vi /etc/systemd/system/isc-dhcp-server.service
Edit the [Service] section:
Restart=on-failure
add RestartSec=5 to instruct systemd to wait 5 seconds before restarting a failed service.
Add the [Install] section which is missing, and add the follow line to it:
WantedBy=multi-user.target
sudo systemctl daemon-reload
sudo systemctl disable isc-dhcp-server
sudo systemctl enable isc-dhcp-server
systemctl status isc-dhcp-server


sudo vi /etc/dhcp/dhcpd.conf
# insert the following and replace with correct MAC address of your device
subnet 10.0.0.0 netmask 255.0.0.0 {
  range 10.0.0.10 10.0.0.200;
  option routers 10.0.0.1;
  default-lease-time 86400;
  max-lease-time 172800;
  host diskstation {
    hardware ethernet XX:11:22:33:44:55;
    fixed-address 10.0.0.10;
  }
#  option domain-name-servers ns1.internal.example.org;
#  option domain-name "internal.example.org";
#  option broadcast-address 10.5.5.31; 
}

#reboot the raspberry pi, reboot the diskstation

# show dhcp leases
cat /var/lib/dhcp/dhcpd.leases

#show isc dhcp service log
systemctl status isc-dhcp-server.service

# following methods can detect IP addresses is up for specified ip range on specified network interface 
nmap -e eth0 -sn 10.0.0.1-254
ping -I eth0 10.0.0.10
for ip in 10.0.0.{10..100}; do ping  -I eth0 -c 1 -t 1 $ip > /dev/null && echo "${ip} is up"; done
ping 10.0.0.10

# check admin page is accessible 
curl -vsL --insecure https://10.0.0.10:5001 2>&1 | grep DiskStation


# to access the diskstation from another client in the network:

# configure a local forward in your .ssh/config
LocalForward 15002 10.0.0.10:5001

#finally be sure to https when accessing dashboard
https://localhost:15002/


# setup IP masquerading. masquerade traffic coming from the 10.0.0/24 subnet (the -s option) to the wlan0 network interface (the -o option).
sudo iptables -t nat -A POSTROUTING -s 10.0.0/24 -o wlan0 -j MASQUERADE