The OSPF Packet Types and Flow

 

<Overview of OSPF Packet Types>

Packet Name	Type / number	Function
Hello	1	- Discovering neighbors  - Maintaining neighbors
Database Description	2	- Summarizing database contents
Link state request	3	- Requesting LSAs (detailed DB)
Link state update	4	- Updating DB
Link state acknowledgment	5	- ACK

 

 

<Topology>

 

 

<OSPF session packet flow>

I got these packet flow after commanding 'clear IP ospf process' on R5

R5#clear ip ospf process Reset ALL OSPF processes? [no]: yes R5# *Feb 11 03:59:26.331: %OSPF-5-ADJCHG: Process 1, Nbr 1.1.4.4 on Ethernet0/0.45 from FULL to DOWN, Neighbor Down: Interface down or detached *Feb 11 03:59:26.335: %OSPF-5-ADJCHG: Process 1, Nbr 1.1.4.4 on Ethernet0/0.45 from LOADING to FULL, Loading Done R5#

ospf_packets.pcapng

0.01MB

 

 

 

<Inital Hello - 75.378121>

 

<DR Hello - 75.379219>

MUST match values.

1. Area ID : 45, matched!

2. Auth password : null, matched!

3. Subnet Mask : /24, matched!

4. Hello/Dead interval : 10/40, matched!

 

<DBD init - 75.379608>

R5 requests LSA lists having route DB data with INIT, MORE, MASTER flags.

 

<DBD more - 75.380375>

R4 answers route lists(LSA) with MORE.

Link State ID has the IP summary.

 

<DBD master - 75.380591>

R5 ack the DBD to R4.

 

<DBD 0x00 - 75.380>

R4 ack to R5 with 0 flags

 

<LS Request - 75.381.448>

R5 request detailed route data about the summarized LSAs

 

<LS Update - 75.382017>

R4 gives detailed updates about LSA routes

 

<LS Update - 75.894438>

R5 sends R5's update for routes.

 

<LS Ack>

R5 and R4 acks to each other about the routes which they have received.