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.

OSPF (Open Shortest Path first)

OSPF

• It is works on Dijkstra Algorithm
•  It is purely a classless protocol
• It supports only VLSM
• It is a 2-layer hierarchy
• Minimizing the routing updates traffic
•  With in the Area only all the information will send to all routers in that area (LSA)
• The ABR will send Auto summary information to the backbone area ( So burden will reduced on the main system)
• The Multi-cast address are

• 224.0.0.5 - All other routers will communicate through this Multicast address.
•  224.0.0.6 - All routers with DR router will communicate through this.
•  NOTE: DR and BDR will Understand both packets from 224.0.0.5/6

• Its AD value is 110
• Its protocol number is 89
• Metric is calculated by using “ BANDWIDTH”
•  Cost of path =  Reference Bandwidth/My outgoing link BW
•  Note: Reference BW in OSPF is 100 Mbps ( We can also change the Reference BW)
•  EX: Serial – 1.54 Mbps = 64 cost, Fast Ethernet - 100Mbps = cost 1, Ethernet – 10Mbps = cost 10

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)

Routing Basics

Routing:

The procedure of connecting two or more different networks

(Or)

The procedure of define routes, protocols and to find best path in them by using algorithms and provide security.

Routing protocol:

It is used to determine the best path for the packets are data to travel from source to destination

Routed protocol:

Which carries the data in the established path is called Routed Protocol. Routed protocols are always assigned to an interface and determine the method of packet delivery.

Ex of routed protocols is TCP, UDP, IP, IPX, SPX, Apple talk.

TCP/IP Utilities

TCP/IP Utilities

it is used to troubleshoot and to maintain a Network without any Problems

• PING (Packet Internet Gopher)

  Ping is used to find the connected device is alive are not. Ping uses a special protocol called ICMP (Internet Control Message Protocol)

  We can check it for Connected devices, websites, DNS, DHCP and Print server etc

• Tracert

It is similar to Ping, it identifies the path through which the packets is going to reach the Destination.

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