How to run script on network address change?

From: Rozhuk Ivan <>
Date: Sun, 20 Jun 2021 16:52:15 +0300

I have FreeBSD 13_at_amd64 router with DHCP client on uplink.

How to run script on IP address change?

I do not see events from devd, only:
!system=IFNET subsystem=em3 type=LINK_DOWN
!system=IFNET subsystem=em3 type=LINK_UP
Received on Sun Jun 20 2021 - 13:52:15 UTC

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