I have an iPhone 6s and an iPad mini 4. Both are running 11.2.5. I also have a TP-Link N600 Dual Band Gigabit ADSL2+ Modem Router (Model No. TD-W8980). The 2.4 and 5 GHz bands have different SSIDs. Issue #1: On both the iPhone and the iPad throughput on the 2.4 GHz network is generally somewhere around 350 Kbps. However, on both devices, throughput on the 5 GHz network is more like what I expect and pay for: from 15 to 20 Mbps. We have multiple devices in the house including two MBAs, two Apple TVs, an iPhone X & 5s, an older iPad mini, a 2017 iMac, a Raspberry PI, etc. No other device is affected by this horrible throughput on the 2.4 GHz band; only my 6s and iPad mini. I have attached photos showing Speedtest results with the X and 6s sitting right next to each other. Once with both on the 2.4GHZ network and once with both on the 5GHz network. Both devices perform as expected on other 2.4GHz networks. To put it simply, I only have throughput problem with these two devices and only when they are on my home 2.4 GHz network. Issue #2: Same two devices. (iPhone 6s & iPad mini 4). Both of these devices frequently have a self-assigned IP address when using public WiFi access points. For example, on Friday I was in a coffee shop that I have visited weekly for several years. On this visit I had to re-enter the WiFi password because I reset the network attempting to solve Issue #1. No matter what I tried I couldn't get a DHCP assigned IP address for either device. I tried forgetting the network, turning WiFi on and off, force restarting both devices, turning WiFi assist OFF on the iPhone. Nothing worked. I had a wander around the restaurant eavesdropping on other people's devices. I observed many different phones, tablets and laptops all successfully connected to the shop's WiFi network. Based solely on that surreptitious survey, me and my devices were the only ones having a problem. I have previously solved this problem at this and other public WiFi APs by manually assigning an IP address based on IP addresses I see or ask about on other devices. (I was too frustrated to bother with this on Friday.) ========== I have sort of solved Issue #1 by turning OFF Auto-Join for the 2.4GHz band on my home LAN. I can sort of solve Issue #2 by entering manual IP addresses for networks where the iPhone and/or iPad refuse to use DHCP. These seem like kludges. Any better suggestions? iPhone 6s and X on home 2.4GHz network. iPhone 6s and X on home 5GHz network.