If you try to establish an OSPF3 with irb interface, the connection might not be formed and stayed in Exstart or Exchange.

root@srxlab> show ospf3 neighbor

ID        Interface       State   Pri  Dead

10.4.0.1     irb.6         ExStart  128   38

The issue is caused because the device is receiving Hello packets, however it's not receiving the Database Description messages.

root@srxlab> show ospf3 statistics

Packet type    Total     Last 5 seconds

     Sent  Received  Sent  Received

 Hello    6    6   1    0 <<<<< Hello messages are communicated bidirectionally

  DbD    12    0   1    0 <<<<< Database Description message are not received

 LSReq    0    0   0    0

LSUpdate    0    0   0    0

 LSAck    0    0   0    0

DBDs retransmitted  :     12, last 5 seconds :

This is a bug that the Dev team is working on to fix it.

You can add the below configuration (interface-type p2p) as a workaround if you don't want to upgrade the OS of a fixed version.

set protocols ospf3 area 0.0.0.0 interface irb.6 interface-type p2p <<<<