OSPF Hellos

OSPF Hello packets discover and maintain relationships with neighbouring OSPF routers.

Hello packets in most default configurations send to the multicast address

Data FieldDescription
Router IDA unique 32-bit ID within the OSPF domain
Authentication OptionsAllows secured communications between OSPF routers. Can be set to: none, clear text or MD5 authentication
Area IDThe OSPF area that the OSPF interface is associated to. It can be in dotted decimal format or as a decimal.
Interface Address MaskThe network mask for the primary IP address associated with the interface that the Hello packet is sourced from
Interface PriorityThe interface priority for OSPF DR elections
Hello IntervalThe interval in seconds that the source router will send out hello packets
Dead IntervalThe interval in seconds that the source router will wait until it declares the neighbour router as down
Designated router and designed backup routerThe IP addresses of the DR and BDR routers in the network link
Active NeighbourA list of OSPF neighbours that have been seen on the network segment
Fields in a Hello packet

The default Hello timer is based on the OSPF network type. The Hello timer can be modified in the interface configuration mode with the command ip ospf hello-interval with a value between 1 and 65535

The dead timer will be modified too as a result of the Hello timer change, but it too can be changed with the command ip ospf dead-interval with a value between 1 and 65535

Make sure that the OSPF dead timer is greater than the hello timer.

Hello and Dead timers can be verified with the command show ip ospf interface

Neighbours timers must match in order for them to become adjacent.



, ,




Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.