Quite a surprise – I was configuring etherchannel on SRX650 to provide redundancy between SRX and EX switch. Quite natural is to use LACP as a control protocol for that. Unfortunately SRX650 does not support LACP on built-in ports. It is supported only on extension cards. You can see LACP counters of received LACP packets increasing but none are sent. That means if you want to build etherchannel with built-in interface (in example in case of extension module failure) you have to build bundle without LACP. It’s not the way I prefer…..