Behavior of Hello OSPF packet

[adnane dakna]

Hello , 

In order to understand how OSPF set up adjacencies , I used wireshark to capture ospf packets under GNS3 Lab , the first packet I saw when I  do shut down and no shut down is Hello unicast Packet , after all Hello packets are mutlicast , I didn't understand why the first hello packet is unicast and How router recognize IP address of other site (neighboor)

[John Blakley]

I believe your first packet is the one above it that goes to 224.0.0.5 (all ospf routers). Then the packet that you see next (the unicast packet) is the unicast hello packet from a router (192.168.15.1) that received the multicast packet from this host (192.168.15.2). Then the adjacency starts to come up with DBD exchange...

HTH,
John

*** Please rate all useful posts ***