BGP LOCAL_PREF is the Second BGP attribute if we dive deep into BGP’s algorithm of best path selection followed by aggregate (detailed in my first post in BGP section). When an AS (autonomous system) has multiple routes to another AS, the LOCAL_PREF indicates the degree of preference for one route over the other routes. The route with the highest LOCAL_PREF value is preferred. You can watch the detailed video on LOCAL_PREF on our : LOCAL_PREF, Weight & MED are often confused with each other. LOCAL_PREF is different from Weight & MED. Unlike weight, LOCAL_PREF is not vendor specific (Weight is Cisco Read More …
Tag: 2b
BGP Weight
BGP Weight is the first BGP attribute if we dive deep into BGP’s algorithm of best path selection followed by Local_Preference & aggregate (detailed in my first post in BGP section). Weight is vendor specific (Cisco proprietary) so it is found only on Cisco routers. Weight is always local on a router and it is not exchanged between BGP routers. The path with the highest weight is always preferred. The range of Weight is 0-65535 and it defaults to 0 always. i.e. The default weight for learned routes is 0 and the default weight for a locally originated route is 32768. We Read More …
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 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 …
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 …