Tag Archives: dhcp

Ubiquiti AirMax – Set radio to use DHCP from command line

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Gain access to radio via ssh

ssh ubnt@192.168.1.20

open up the /tmp/system.cfg

vi /tmp/system.cfg

Delete the following line. To move the cursor to the following line and type “dd” and vi will delete the whole line.

dhcpc.status=disabled

Add the following 5 lines. Hit “i” to enter vi insert mode.
br0 should be correct interface in most scenarios.

dhcpc.1.devname=br0          
dhcpc.1.fallback=192.168.1.20         
dhcpc.1.fallback_netmask=255.255.255.0
dhcpc.1.status=enabled      
dhcpc.status=enabled

Save the file by hitting esc and then “:wq” followed by Return/Enter

Save the config changes and reboot the radio so it pulls an address.

/usr/etc/rc.d/rc.softrestart save && reboot

Setup DHCP server on Linux

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Install dhcp server software

sudo apt install isc-dhcp-server

Edit the following config file and set the networking interface it should use. In this case enp60s0

sudo vi /etc/default/isc-dhcp-server

Example line to change

INTERFACESv4="enp60s0"

Now edit the dhcpd.con file 

sudo vi /etc/dhcp/dhcpd.conf

Add the following in. Change the addresses and settings as needed.

subnet 192.168.47.0 netmask 255.255.255.0 {
   range 192.168.47.26 192.168.47.30;
   option domain-name-servers ns1.internal.example.org;
   option domain-name "internal.example.org";
   option subnet-mask 255.255.255.0;
   option routers 192.168.47.1;
   option broadcast-address 192.168.47.255;
   default-lease-time 600;
   max-lease-time 7200;
 }

Set a static ip on the computer that’ll be acting as the dhcp server. You can set it as the gateway if it is the gateway.

Allow dhcp through the firewall 

sudo ufw allow  67/udp
sudo ufw reload
Restart the service and connect a client.

sudo systemctl restart isc-dhcp-server

More info.

You can look at dhcp leases with the following command

tail -f /var/lib/dhcp/dhcpd.leases