IS-IS Protocol has two types of nodes (since the roots of IS-IS are based on ISO Connectionless Network Protocol) i.e. IS & ES. ES (End System): A workstation or network host (limited routing capability) IS (Intermediate Systems): Network devices such as routers with full packet-forwarding capabilities. The word intermediate refers to the capabilities of routers as intermediate forwarding or relay devices. These are also referred to as gateway in some older networking literature of ISO *If these terms are new to you, I would recommend to review the IS-IS terminology & basics at ATech before proceeding further at: A brief flashback of IS-IS – Part I Read More …
Category: Link State Routing Protocols
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 backbone/Non-backbone. A virtual link does not have ABR physical Connectivity to Backbone till to configure virtual link between non-backbone area and Backbone. In between two routers, a virtual link can be configured, that have an interface to a single common Transit/Non-backbone area but it can’t Read More …
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 on white-list then he/she is allowed the access, otherwise the access is rejected simply. Types of OSPF Authentication OSPF supports two types of authentication i.e. Plain Text authentication and Message Digest 5 (MD5) authentication. As a message/packet required authentication for both destinations. Read More …
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 neighbors, and help them by sharing their information & tasks. Similarly, in Network & routing world there is a difference in neighborship & adjacency. OSPF neighbourship is straightforward while IS-IS needs a bit deeper thought to get it fully. Lets take a closer look at both. For OSPF, in order to form OSPF adjacencies, the following must match on the neighboring routers: Read More …
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 …