Editing Open Shortest Path First (section)

=== Hello Packet ===
{| class="wikitable  floatright mw-collapsible mw-collapsed" style="width: 400px;"
|+ OSPF v2 hello packet, field lengths in bytes
|-
! 24
! 4
! 2
! 1
! 1
! 4
! 4
! 4
! 4
|-
| rowspan="2" colspan="1" | '''Header'''
|-
| Network Mask
| Hello Interval
| Options
| Router Priority
| Router Dead Interval
| Designated Router ID
| Backup Designated Router ID
| Neighbor ID 
|}

{| class="wikitable  floatright mw-collapsible mw-collapsed" style="width: 400px;"
|+ OSPF v3 hello packet, field lengths in bytes
|-
! 16
! 4
! 1
! 3
! 2
! 2
! 4
! 4 
! 4 
|-
| rowspan="2" colspan="1" | '''Header'''
|-
| Interface ID
| Router Priority
| Options
| Hello Interval
| Router Dead Interval
| Designated Router ID
| Backup Designated Router ID
| Neighbor ID
|}
OSPF's Hello messages are used as a form of greeting, to allow a router to discover other adjacent routers on its local links and networks. The messages establish relationships between neighboring devices (called adjacencies) and communicate key parameters about how OSPF is to be used in the autonomous system or area. During normal operation, routers send hello messages to their neighbors at regular intervals (the ''hello interval''); if a router stops receiving hello messages from a neighbor, after a set period (the ''dead interval'') the router will assume the neighbor has gone down.