Wireshark Operators

Wireshark is the most useful & popular tool for packet Level deep Network Analysis & Troubleshooting. Most importantly, it is open source. It is like a measuring meter or device to find and examine what is going on inside a network cable or port just like a multimeter is used by an electrician to examine […]

OSPF Virtual Links

Virtual Link is a non-Physical connectivity or link. As we know OPSF must be connected with Backbone Area0 but sometime it becomes difficult due to some reasons. So there we required Virtual Links for logical connection to Backbone. Also known as logical link which uses in least cost path connectivity between routers or ABR or […]

OSPF Authentication

What is Authentication: Authentication is the mechanism of recognizing the identity of a user. Associating an incoming request with a set of identifying credentials is called Authentication.    The credentials provided are compared to those in the database of the authorized user’s information register on a local operating system or somewhere remote. If the user is […]

Yet another difference b/w IS-IS and OSPF

Neighbour is someone who lives nearby, normally in a house or apartment that is next door or, in the case of houses, across the street. Some neighbors are adjacent while some are not. People form friendships with their neighbours, and help them by sharing their information & tasks. Similarly, in Network & routing world there […]

OSPF Type5 Message / LSAck Packet (Link State Acknowledgment)

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 […]

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 […]

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 […]

OSPF Type2 Message / DBD Packet (Database Descriptor)

DBD (Database Description or Type2 OSPF Packet) is a sort of summary of the OSPF Database in a router. DBD is used to check if the LSDB between 2 routers is the same. These packets are exchanged when an adjacency is being initialized. They describe the topology information a router has in its database. DBD […]