Beginning on Nov 12, several devices on our network are having their (static) DHCP addresses deassigned and immediately reassigned every few hours, intermittently, despite the standard 3-day lease length. Here is the log of the most recent incident (MAC addresses changed, obviously):
Nov 30 08:47:56 33Comm LAN-DHCP deassigned 192.168.151.244 from aa:aa:aa:aa:aa:aa
Nov 30 08:47:56 33Comm LAN-DHCP assigned 192.168.151.244 to aa:aa:aa:aa:aa:aa
Nov 30 08:48:00 33Comm LAN-DHCP deassigned 192.168.151.247 from dd:dd:dd:dd:dd:dd
Nov 30 08:48:00 33Comm LAN-DHCP assigned 192.168.151.247 to dd:dd:dd:dd:dd:dd
Nov 30 08:48:00 33Comm LAN-DHCP deassigned 192.168.151.245 from bb:bb:bb:bb:bb:bb
Nov 30 08:48:00 33Comm LAN-DHCP assigned 192.168.151.245 to bb:bb:bb:bb:bb:bb
Nov 30 08:48:00 33Comm LAN-DHCP deassigned 192.168.151.246 from cc:cc:cc:cc:cc:cc
Nov 30 08:48:00 33Comm LAN-DHCP assigned 192.168.151.246 to cc:cc:cc:cc:cc:cc
...
Nov 30 12:48:56 33Comm LAN-DHCP deassigned 192.168.151.244 from aa:aa:aa:aa:aa:aa
Nov 30 12:48:56 33Comm LAN-DHCP assigned 192.168.151.244 to aa:aa:aa:aa:aa:aa
Nov 30 12:49:00 33Comm LAN-DHCP deassigned 192.168.151.246 from cc:cc:cc:cc:cc:cc
Nov 30 12:49:00 33Comm LAN-DHCP assigned 192.168.151.246 to cc:cc:cc:cc:cc:cc
Nov 30 12:49:00 33Comm LAN-DHCP deassigned 192.168.151.247 from dd:dd:dd:dd:dd:dd
Nov 30 12:49:00 33Comm LAN-DHCP assigned 192.168.151.247 to dd:dd:dd:dd:dd:dd
Nov 30 12:49:01 33Comm LAN-DHCP deassigned 192.168.151.245 from bb:bb:bb:bb:bb:bb
Nov 30 12:49:01 33Comm LAN-DHCP assigned 192.168.151.245 to bb:bb:bb:bb:bb:bb
At the same time that this occurs, current connections (e.g., VoIP, Skype) on these devices drop.
Relevant settings (export compact):
/ip pool
add name=LAN-pool ranges=192.168.150.100-192.168.151.249
/ip dhcp-server
add add-arp=yes address-pool=LAN-pool authoritative=yes disabled=no interface=\
ether1-LAN name=LAN-DHCP
/ip dhcp-server network
add address=192.168.150.0/23 dns-server=192.168.150.1 gateway=192.168.150.1 \
netmask=23 ntp-server=10.0.1.13
/ip dhcp-server lease
add address=192.168.151.244 client-id=1:c0:3f:e:10:21:7b mac-address=aa:aa:aa:aa:aa:aa server=LAN-DHCP
add address=192.168.151.245 client-id=1:0:e:8:d9:a9:11 mac-address=bb:bb:bb:bb:bb:bb server=LAN-DHCP
add address=192.168.151.246 client-id=1:0:e:8:d7:60:34 mac-address=cc:cc:cc:cc:cc:cc server=LAN-DHCP
add address=192.168.151.247 client-id=1:0:e:8:d8:4c:fb mac-address=dd:dd:dd:dd:dd:dd server=LAN-DHCP
Pretty straightforward, I think. I am not sure if this is caused by the dhcp-server system (e.g., changes made for 5.21) or something else; Hopefully, this will help someone track down the problem. If anyone has any insight into this, or this issue has been seen before, please let me know!
Since I am on the verge of losing a customer due to this behavior, I am going to try giving these devices static IPs (manually, not using dhcp-server) and see if that eliminates the drops. Since this will suggest whether the problem is within the dhcp-server system or elsewhere, I will follow up with my own results next week.
EDIT: This is on a RB750UP, currently running ROS 5.22. Upon further perusal of the logs, this deassign-reassign pattern goes back years–but this is the first time I have noticed it happening with static leases, and with devices for which it causes the user a real inconvenience.