AirOS uses udhcpc for the DHCP client on Ubiquiti Radios. To renew the DHCP address you can kill the udhcpc process and it’ll automatically restart and get a new address.
Renew DHCP lease
Kill udhcpc with the following command.
Print info about the DHCP lease. May need to change “info.br1” to “info.eth0” or some other interface.
XW.v6.2.0# cat /etc/udhcpc/info.br1
Command arguments that udhcp is run with. Info was collected by running the “ps | grep udhcp” command. Note that the interface “eth0” can be different if the device is in bridge mode.
/sbin/udhcpc -f -i eth0 -s /etc/udhcpc/udhcpc -p /var/run/udhcpc.eth0.pid -h device_name
udhcpc help output
XW.v6.2.0# udhcpc --help
BusyBox v1.24.2 (2019-07-03 11:13:35 EEST) multi-call binary.
Usage: udhcpc [-fbqvRB] [-t N] [-T SEC] [-A SEC/-n]
[-i IFACE] [-s PROG] [-p PIDFILE]
[-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]...
-i,--interface IFACE Interface to use (default eth0)
-s,--script PROG Run PROG at DHCP events (default /usr/share/udhcpc/default.script)
-p,--pidfile FILE Create pidfile
-B,--broadcast Request broadcast replies
-t,--retries N Send up to N discover packets (default 3)
-T,--timeout SEC Pause between packets (default 3)
-A,--tryagain SEC Wait if lease is not obtained (default 20)
-n,--now Exit if lease is not obtained
-q,--quit Exit after obtaining lease
-R,--release Release IP on exit
-f,--foreground Run in foreground
-b,--background Background if lease is not obtained
-S,--syslog Log to syslog too
-r,--request IP Request this IP address
-o,--no-default-options Don't request any options (unless -O is given)
-O,--request-option OPT Request option OPT from server (cumulative)
-x OPT:VAL Include option OPT in sent packets (cumulative)
Examples of string, numeric, and hex byte opts:
-x hostname:bbox - option 12
-x lease:3600 - option 51 (lease time)
-x 0x3d:0100BEEFC0FFEE - option 61 (client id)
-F,--fqdn NAME Ask server to update DNS mapping for NAME
-V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')
-C,--clientid-none Don't send MAC as client identifier
USR1 Renew lease
USR2 Release lease
Note that you can also send a signal to the PID of udhcpc and have it renew the address. To do that use the following command, replacing pidofudhcpc to pid of udhcp.
kill -s USR1 pidofudhcpc
or use the following command to find the pid for you.
kill -s SIGUSR1 $(pgrep udhcpc)