New Training: Advanced IS-IS Foundations
In this 10-video skill, CBT Nuggets trainer Knox Hutchinson explores deeper theoretical understandings of IS-IS on Junos devices. Watch this new Juniper training.
Learn Juniper with one of these courses:
Service Provider Routing and Switching Professional
This training includes:
1.4 hours of training
You’ll learn these topics in this skill:
Introducing Advanced IS-IS Foundation
Multi-Level IS-IS Refresher
IS-IS Packet Types
Basic Multi-Level IS-IS Deployment on JUNOS
LSPDU Contents and Common TLVs
PDU Flooding and Mesh Groups
Validating IS-IS Config and LSDB
Summarizing Advanced IS-IS Foundations
What is An IS-IS Hello Packet?
IS-IS is an interior gateway protocol (IGP) available on Juniper networking equipment. Much like OSPF, it's a link-state-based IGP. It's preferred over OSPF due to its inherent security and modularity, though. Likewise, much like OSPF, it uses something called a 'Hello' packet for discovery.
A 'Hello' packet is a broadcast packet used to discover the identity of neighboring networking devices. It uses these packets to determine if other devices are level 1 or level 2 intermediate devices.
These 'Hello' packets come in three forms:
Point-to-Point hello packets
Level 1 broadcast links
Level 2 broadcast links
It should be noted that level 1 routers have to share the same area address to form an adjacency. Level 2 routers do not have that limitation.
The length of each 'Hello' packet is preset. IS-IS routers do not resize these packets. Instead, each interface supports the maximum packet size of 1492 bytes. Packets are padded to meet this size.
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