OSPF Type1 Message / Hello Packet

Hello packet, also called Type1 OSPF Packet, is a special packet/message that is sent out periodically from a router to establish and confirm network adjacency relationships. These packets are sent periodically on all interfaces in order to establish and maintain neighbor relationships.

Hello Packets contain different parameters including Network mask, Hello Interval and Router Dead Interval,…. These parameters are needed to form neighbor relationships. All routers connected to a common network (NBMA,…) must agree on certain parameters. Below is the detailed description of Hello Packet & its fields:

 

Below is description of fields in the OSPF Hello Packet:

 

 

Consider the simple below topology with two Routers:

As soon as we enable OSPF on the router interfaces, it starts exchanging Hello Packets.

It is obvious from the below detail, spend some time with it to understand it fully:

OSPF Packets - 1. Hello

We can see from the above capture that OSPF Hello Packets are defined as Type1 in the header frame. Both Routers are exchanging the Hello Packets once the OSPF has been enabled & configured properly.

 

 

Written by 

Waqas Karim is a seasoned Network Expert … Geek. He is the founder of ATech. ATech was started for learning & sharing. Over time the platform has grown to include other resources which continue to attract fellow networkers. Today it sees upward trend of a hundred thousand visitors per month, scattered all over the globe. His specialty is networking, but his interest & expertise spans from traditional IT to Network Security including Programming, Virtualization, Service Provider & so on... no matter the badge on the box. He is CCIE Certified (CCIE#56732) in addition to below badges: Telecom Engineer (BE) + CCIE-RS (CCIE#56732) + Huawei Certified (HW#706632) + MBA Microsoft Certified MCITP, MCSE#109*26, CCNP-Sec, CCNP-SP, CCNA-DC, CompTIA Security+, Nokia NRS-I, JNCIA, ITIL Certified (ITIL#*6373), CEH (Certified Ethical Hacker).

avatar
10 Comment threads
7 Thread replies
0 Followers
 
Most reacted comment
Hottest comment thread
3 Comment authors
Wyman JarrWaqas KarimfurtdsolinopvObbiWaqas Karim Recent comment authors
  Subscribe  
newest oldest most voted
Notify of
Wyman Jarr
Guest
Wyman Jarr

How does the OSPF router know the neighbor’s interface address in the LAN ?

furtdsolinopv
Guest
furtdsolinopv

Pretty element of content. I just stumbled upon your blog and in accession capital to claim that I get in fact loved account your blog posts. Anyway I’ll be subscribing in your feeds or even I fulfillment you get admission to constantly quickly.

Obbi
Guest
Obbi

Nice one

Joly Ken
Guest
Joly Ken

Thank you for helping me in hello packets.

Joly Ken
Guest
Joly Ken

Is hello pack behave as same as IEGRP

Jassi
Guest
Jassi

Thank you for the awesome explanation.

Ganesh
Guest
Ganesh

Thank you very much for starting this tutorial..I request to please continue it. Thanks.

Aditya. Jain
Guest
Aditya. Jain

First step of Levels? Good!

Chandar
Guest
Chandar

I’m also studying ospf type messages, its helps to understand behavior of a hello message in ospf.

Luxman. Rathod
Guest
Luxman. Rathod

Nice post