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 …
Tag: 2b
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 …
OSPF Packet Types
There are different OSPF Packet Types which are used for different purposes. We know that OSPF routers need to perform different duties in order to route traffic. e.g. establish and maintain adjacencies, send and receive requests, ensure reliable delivery of Link State advertisements (LSAs) between neighbors and to describe Link State Databases. All these duties are performed using messages/Packets. Only one type of message/packet cannot perform all these duties. So, different types of messages/Packets are needed. OSPF has five types of Packets in total which are listed in below. Each type of packet has its own duties to perform. All these Read More …
Network statements in Lazy mode & Deep dive into OSPF Network command
During my journey of CCIE, I noticed an OSPF feature worth of sharing. In Core/IGP routing, instead of typing a lot in network commands in OSPF, we can just use network 0.0.0.0 255.255.255.255 and more surprisingly 0.0.0.0 0.0.0.0. Once you enter all zeroes, running-config will convert it to quad 0 followed by quad 255. We can also use 0.0.0.0 0.0.0.0. It just includes all interfaces the same way as if you do 0.0.0.0 255.255.255.255. Below is the practical demonstration: If the router has all interfaces in a single area, I always use network 0.0.0.0 255.255.255.255 area area-id. Since, Read More …
OSPF in a Nutshell
Below are some of the OSPF edges/pros as compared to contemporary protocols of the same age: No hop count limitations as in other contemporary protocols OSPF allows summarization with almost all possible scenarios Recognizes VLSMs (variable-length subnet masks) No Broadcasts … OSPF uses multicasts 224.0.0.5, 224.0.0.6 OSPF converges much faster than RIP, because OSPF propagates changes immediately. Load balancing up to 6x equal cost paths OSPF is a Secure Protocol (Multiple authentication options available) OSPF allows for tagging of external routes injected by other AS OSPF is CPU/Memory intensive especially in multi-area and multi-process scenarios Summarization can be done only Read More …