One of the important issues that makes OSPF neighbor hangs on (Exstart state) is that a router is trying to make adjacency with a non DR/BDR on a segment. Offcourse those typically applied for NBMA & Broadcast OSPF Networks.
PLS try to influence the prioity at the interface level command to force the DR/BDR election.
NOTE: You may clear the OSPF process or reboot the router for the new election.
EDIT>> Here is absolute case for the Exstart OSPF neighbor state:
If you are configuring OSPF Over NBMA and hardcoding the command (IP OSPF Network point-to-multipoint) on the Hub & Spokes, Please make sure you remove all L3-to-L2 mapping from all router interfaces.
The fact that OSPF treats all links as acollection of Point-to-Point links typically possible when changing the Network type of the interface by (IP OSPF Network point-to-multipoint), by doing so, its dynamically discovering neighbors & it creats by itself L3-to-L2 maps for the neighbors , therfore , avoid static mapping which causes this problem.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...