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 what is going on inside an electric cable … but of course at much deeper level. Wireshark or such SW tools are not something very new. Such tools were available in the past as well but they were very expensive and proprietary because they were mostly Read More …
Category: Networking -Others
IS-IS TLV’s
TLV (Type-Length-Value or Tag-Length-Value) is an encoding scheme used for optional information element in a certain protocol. The type and length are fixed in size (typically 1-4 bytes), and the value field is of variable size. Type: It is simply the data being processed, a binary code, often simply alphanumeric, which indicates the kind of field that this part of the message represents. Length: It specifies the length/size of the value field, typically in bytes Value: Variable-sized series of bytes which contains data for this part of the message. It is the third field and contains a “length” amount of data representing the value for Read More …
IS-IS Levels & Relationships
IS-IS creates flooding boundaries logical by breaking the network into routing domain levels i.e. A level2 routing domain and multiple level1 routing domains. The single Level 2 routing domain could be analogous to OSPF Area0 and multiple Level 1 routing domains are analogous to other OSPF Areas. Basically, IS-IS has two layer hierarchy: Level-2 (the backbone) Level-1 (the areas) This two layer hierarchy is achieved by dividing the routers (IS’s) into three types called L-1, L-2, L-1-2 IS’s. Level1 Router is analogous to OSPF Internal non-backbone router (Totally Stubby). It contains a level1 LSDB only and is responsible for only routing Read More …
A brief flashback of IS-IS – Part II
Hello PDU’s of IS-IS: IS-IS has three types of Hello PDUs: i. ESH (ES Hello – sent by ES to an IS) ii. ISH (IS Hello – sent by IS to an ES) iii. IIH (IS-IS Hello – sent between two ISs) Routing Levels Level0: Used to locate end systems Level1: Routing within an area Level2: Backbone between areas Level3: Inter-AS routing NSAP Addressing IS-IS uses the NSAP address for communication. Each router in IS-IS is identified with an ID called NET (Network Entity Title) same as Router ID which is NSAP address. Below is the NSAP addressing format: Read More …
Adjacencies in IS-IS
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 …