OSPF area types

For previous post about LSA types in OSPF...Click here lsa-types-in-ospf

OSPF area types:

1. Backbone area (area 0)
2. Standard area
3. Stub area
4. Totally stubby area
5. Not-so-stubby area (NSSA)

Note: The concept of Areas is to compress the LSA’s. so as to reduce the Traffic in Network.

     Let's begin by examining a standard area. Note that the backbone area is essentially a standard area which has been designated as the central point to which all other areas connect, so a discussion of standard area behavior largely applies to the backbone area as well.

Standard Areas:

LSA Types in OSPF

For previous post about DR and DBR in OSPF...Click here...dr-and-bdr-concepts-in-ospf

LSA Types in OSPF

OSPF relies on several types of Link State Advertisements (LSAs) to communicate link state information between neighbours. A brief review of the most applicable LSA types:

LSA Types:

• Type 1 - Represents a router
• Type 2 – Network LSA (who is my DR)
• Type 3 - A network link summary all ABR (internal route)
• Type 4 - Represents an ASBR (who is my ASBR)
• Type 5 - A route external to the OSPF domain
• Type 6 – Group membership Multicasting
• Type 7 - Used in stub areas in place of a type 5 LSA

DR and BDR Concepts in OSPF

For previous post about Neighbourship formation....Click here neighbour-formation-stages-in-ospf

àIn a network all the router will sends route updates to all other routers, so that the burden is very high on the network due to the routing updates traffic. 

      To solve this DR and BDR is introduced. So that all the routers will send route updates to these DR and BDR only

Ø  To reduce the FULL Neighbourships.

Ø  To reduce the CPU burden on devices.

Ø  To reduce the Bandwidth utilization.

So that all routers will make FULL Neighbourship with DR, while the other router will make up to 2-Way state neghbourship only.

Neighbour Formation Stages in OSPF

Previous post about OSPF... click here open-shortest-path-first.

Neighbour Formation Stages in OSPF

1. Down stage	It is attempt stage/ starting stage         This is the first OSPF neighbour state. It means that no information (hellos) has been received from this neighbour, but hello packets can still be sent to the neighbour in this state.
2. Init	This state specifies that the router has received a hello packet from its neighbour, but the receiving router's ID was not included in the hello packet. When a router receives a hello packet from a neighbour, it should list the sender's router ID in its hello packet as an acknowledgment that it received a valid hello packet.
3. 2-Way stage	This state designates that bi-directional communication has been established between two routers. Bi-directional means that each router has seen the other's hello packet.        At tilohe end of this stage, the DR and BDR for broadcast and non-broadcast multi-access networks are elected.

Enhanced Interior Gateway Routing Protocol

EIGRP (Enhanced Interior Gateway Routing Protocol) it is derived from IGRP

IGRP is a Distance vector routing protocol.

·         EIGRP is a Hybrid (or) Advance distance vector routing protocol

·         The AD value of EIGRP is

·         90     (EIGRP-INTERNAL),

·          170     (EIGRP-EXTERNAL)

·         Protocol  number is 88

·         It works on RTP (Reliable transport protocol)

·         It is fast convergence

·         It works as class full/ classless (no auto summary)

·         It works on AS number  (Autonomous system)  {in order to form neighbor ship the AS number should match}

·         Fast convergence

·         100% loop Free

RIP (Routing Information Protocol)

Rip is a distance vector protocol

•  How far and in which direction the route presents (no:of Hops between the source and destination)

Distance vector protocol:

The name distance vector is derived from the fact that routes are advertised as vectors of (distance, direction), where distance is defined in terms of a metric and direction is defined in terms of the next-hop router. For example, "Destination A is a distance of 5 hops away, in the direction of next-hop router X." As that statement implies, each router learns routes from its neighboring routers' perspectives and then advertises the routes from its own perspective. Because each router depends on its neighbors for information, which the neighbors in turn may have learned from their neighbors, and so on, distance vector routing is sometimes facetiously referred to as "routing by rumor."

1.      In rip max hop count is 15
2.      Rip AD value is 120
3.      It runs on UDP
4.      Protocol number 520

Dynamic Routing & Administrative Distance (AD)

Dynamic Routing is again subdivided into two types:

a)      IGP – it will exchange private network information within the AS

b)      EGP – it will exchange public network information within the AS

Exterior Gateway Protocol (EGP)                       Interior Gateway Routing Protocol (IGP)

* BGP (Border Gateway Protocol)                             * RIP (Routing Information Protocol)

* EIGRP (Enhanced Interior Gateway Routing Protocol)

* OSPF (Open Shortest Path First)

                       

Administrative Distance (AD Values):

Depends on the AD value router will prefer the Routes (Thrust worthiness)

Basics of Networking

What is Network:

It is a group of connected devices to share data, information and to communicate with each other.

What is Networking:

            The process of configuring networking devices to make a network for communication is called networking.

Networking devices are 

• Hub
• Bridge
• Switch and
• Router...etc