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Expected Behaviour:
DHCP offers should be accepted by any client
Actual Behaviour:
Clients repeatedly ask for DHCP addresses, every 3 seconds, overwhelming pi-hole and slowing all responses (including DNS). Some devices (iPhone) can be observed to temporarily acquire an address, and then drop it moments later.
Debug Token:
eepv3gugqb
Versions:
FTL Version v4.1.2
Linux pi-hole 4.14.79+ #1159 Sun Nov 4 17:28:08 GMT 2018 armv6l GNU/Linux
Raspbian GNU/Linux 9 (stretch)
Config notes:
pi-hole is configured for DNS and DHCP, on subnet 192.168.2.1/24. It is configured to grant infinite leases from 192.168.2.129 to 192.168.2.223, and most expected devices are allocated static leases below this range.
Example:
Dec 28 08:35:18 dnsmasq-dhcp[882]: DHCPDISCOVER(wlan0) 44:61:32:xx:xx:xx
Dec 28 08:35:18 dnsmasq-dhcp[882]: DHCPOFFER(wlan0) 192.168.2.26 44:61:32:xx:xx:xx
Dec 28 08:35:18 dnsmasq-dhcp[882]: DHCPREQUEST(wlan0) 192.168.2.26 44:61:32:xx:xx:xx
Dec 28 08:35:18 dnsmasq-dhcp[882]: DHCPACK(wlan0) 192.168.2.26 44:61:32:xx:xx:xx ecobee3
Dec 28 08:35:21 dnsmasq-dhcp[882]: DHCPREQUEST(wlan0) 192.168.2.26 44:61:32:xx:xx:xx
Dec 28 08:35:21 dnsmasq-dhcp[882]: DHCPACK(wlan0) 192.168.2.26 44:61:32:xx:xx:xx ecobee3
...
Dec 28 08:36:23 dnsmasq-dhcp[882]: DHCPREQUEST(wlan0) 192.168.2.58 68:c6:3a:xx:xx:xx
Dec 28 08:36:23 dnsmasq-dhcp[882]: DHCPACK(wlan0) 192.168.2.58 68:c6:3a:xx:xx:xx PurpleAir_751
Dec 28 08:36:26 dnsmasq-dhcp[882]: DHCPREQUEST(wlan0) 192.168.2.58 68:c6:3a:xx:xx:xx
Dec 28 08:36:26 dnsmasq-dhcp[882]: DHCPACK(wlan0) 192.168.2.58 68:c6:3a:xx:xx:xx PurpleAir_751
Dec 28 08:36:28 dnsmasq-dhcp[882]: DHCPREQUEST(wlan0) 192.168.2.58 68:c6:3a:xx:xx:xx
Dec 28 08:36:28 dnsmasq-dhcp[882]: DHCPACK(wlan0) 192.168.2.58 68:c6:3a:xx:xx:xx PurpleAir_751
Notes:
Testing with nmap reveals unexpected behavior, where lease time is set to the minimum dnsmasq time (2 mins):
Starting Nmap 7.70 ( https://nmap.org ) at 2018-12-28 08:12 PST
Pre-scan script results:
| broadcast-dhcp-discover:
| Response 1 of 1:
| IP Offered: 192.168.2.148
| DHCP Message Type: DHCPOFFER
| Server Identifier: 192.168.2.10
| IP Address Lease Time: 2m00s
| Renewal Time Value: 1m00s
| Rebinding Time Value: 1m45s
| Subnet Mask: 255.255.255.0
| Broadcast Address: 192.168.2.255
| Domain Name Server: 192.168.2.10
| Domain Name: xxxxxxxx
|_ Router: 192.168.2.1
WARNING: No targets were specified, so 0 hosts scanned.
Nmap done: 0 IP addresses (0 hosts up) scanned in 4.23 seconds