Finally, Acknowledgements are needed once the LSR/LSU (request/reply) process is complete. Type5 OSPF Packets are used for this purpose which are called LSAck (Link State Acknowledgment). Consider the simple below topology with two Routers: After LSU’s, LSAck’s are sent as a confirmation message. It is obvious from the below detail, spend some time with it to understand it fully:
Tag: Link State Request
OSPF Type4 Message / LSU Packet (Link State Update)
Similar to LSR, LSU (Link State Update) is the response/reply to LSR. Each Link State Update packet carries a collection of link state advertisements one hop further from its origin. Consider the simple below topology with two Routers: LSU’s are generated in response to the LSR’s. It is obvious from the below detail, spend some time with it to understand it fully:
OSPF Type3 Message / LSR Packet (Link State Request)
LSR (Link State Request / Type3 OSPF Packets) is simply a request as obvious from its name. After DBD phase for first time, routers keep on sending LSR to keep the LSDB in sync. Consider the simple below topology with two Routers: After the Hello & DBD, Requests are made from Routers to query the missing Database Parts. It is obvious from the below detail, spend some time with it to understand it fully:
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: Read More …
OSPF Packet Formats
There are different OSPF Packet Types which are used for different purposes. OSPF has five types of Packets. OSPF uses its own protocol and doesn’t use a transport protocol like TCP or UDP. It uses IP Protocol 89. Let us have a detailed look into each type of Packet now. Below is a general view of OSPF Packet. When changing from one type to another in above five categories, just the TYPE & DATA fields are changed. This is how it will look when we deep dive into the packet itself. Below are the five types of Packets in detail Read More …