Excessive DHCP renewals

[JohnVitz]

In reviewing my router logs, I have one attached device that gets a DHCP renewal about every few minutes and sometimes even seconds apart. The device is an iPhone 7. The other 3 iPhones in the house renew their ip addresses infrequently. As one might expect, the router shows a DHCP event that coincides with entering the network after being away (work, school, etc). Below is a tiny fraction of the router log for today.

This does not apprear to be normal behavior. I've checked the iPhone configuration against the other iPhones and its settings are identical. 

[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:40:06
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:38:05
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:38:03
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:38:01
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:38:01
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:23:18
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:23:17
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:08:33
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 04:08:33
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 03:53:50
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 03:53:49
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 03:39:05
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 03:39:04
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 03:24:19
[DHCP IP: 10.247.10.78] to MAC address bc:9f:ef:16:73:c9, Sunday, October 15, 2017 02:57:21

[shadowsports]

Since other devices appear to be working correctly and it's only the one iPhone, I would try resetting the network on the device (you'll be prompted to restart)  and see what happens when it reconnects with the router.  

I would also ensure it (the iPhone) is not running any apps that send packets to the network, like "keep alive" or something different from the other phones that connect normally.  Might be something simple you've not considered or overlooked.