OSPF packet capture queries

[RobotAjay]

I am configuring OSPF and while running packet captures I see at times hello packets are sent via unicast also I could see a few LS update packets are sent to a multicast address(as destination), may I know under what condition this happens?

Thanks in advance.

[MHM Cisco World]

Hello send as multicast 

 it send as unicast 

If you use virtual link

If you use neighbor under ospf (mostly use when we have NBMA)

MHM

[Torbjørn]

OSPF packets are exhcanged as unicasts for statically configured neighbors.

No hello packets are exchanged between members of virtual links(unless directly connected - then they will send regular multicast packets unless configured statically).

OSPF routers use unicast packets during extart/exchange and loading phases. After this they will transition to using multicast packets as usual. This reduces the amount of network traffic used for these traffic-heavy exchanges.