I am going nuts. Hardware Linksys WRT 3200 ACM with latest openwrt. I have about 30 ESP8266 devices and 3 Raspberry PIs in my network. All ESP8266 connect and get DHCP, so does my Chromebook. Linux devices, including Raspberry PIs won't get DHCP leases. 2.4 Ghz 'n' mode only.
The very same hardware with stock OS works (more or less) ok, it also works fine with a Zyxel Armor Z2 and their version of *Wrt. I installed openwrt on the Linksys to get more flexibility. DHCP works fine if Raspberry PI is hard wired.
tcpdump confirms the the bootp is broadcasted. I have "unknown DSAP" entries (0x62, 0x64) on the tcpdump which may indicate WPA/WPA2 encrypted answers, but whatever they are, Linux seems unable to deal with them. I also see plain text arp requests in the dump, which confuses me even more.
Log on the openwrt shows no incoming requests though.
EDIT: Forcing tkip on the openwrt/linksys makes the wifi going on and off.
Out of options.