Plumbing the internet

OSPF area types allow networks to be segmented into smaller areas to reduce the amount of routing information that needs to be exchangedThe backbone area is the central area of the OSPF network and must exist in every OSPF network. Standard areas are connected to the backbone area and have their own LSDBs, while stub areas and NSSAs block external routing information to reduce the amount of routing information exchanged between areas. Totally stubby areas block both external and inter-area routes. Routers within the same area share the same LSDB and use it to calculate the shortest path to a destination network. OSPF defines several types of areas, each with different functions and characteristics below are the OSPF area types and their operations: Backbone Area (Area 0) - The backbone area (also called Area 0 - area id must be 0 / 0.0.0.0 in 32bit notation) is the central area of an OSPF network and it must exist in every OSPF multiarea network. All other areas must be connected to th...

  > Topology Overview: - Routers RG 31/32 - peering routers  - Routers RR-10 / RR-20 - route reflectors - Ps and PEs - core and customer connectivity BGP CONCEPTS > Pourpouse of BGP: - interconnect between different AS (interdomain communication) - widely used in Service Provider, Large Enterprise and Datacenter enviroments - multihomed customers - scalable  - created with stability in mind > Main considerations - trust one one - eBGP filter advertisment in and out  - policy based  - multiprotocol support IPv4/6, VPNv4/6 and VXLAN - reliable updates - triggered updates only - uses rich metrics/attributes > Internal BGP - neighbourship between two nodes in the same AS - AS-PAth is not updated when sending to iBGP - BGP Split-horizon is used to prevent the loops, iBGP updates are not forwarded to any other iBGP peer - BGP next-hop is not changed - used to carry partial of full table of internet routing prefixes > External BGP - neigborship between t...

What is IS-IS? - it is a link state protocol which originates from ISO 10589 - Connectionless Network Protocol (CLNP) - was originally designed to support CLNS, still uses CLNS for its transport - supports both IPv4 and IPv6 - mostly popular in large ISP environments  - similarly to OSPF it runs Dijkstra SPF algorithm - use Hello packets to manage adjacencies (IIHs) - use areas and two-level hierarchy, only two types of the areas  - summarisation is only possible on ABRs between areas  - elects designated router (DIS) similar to OSPF DR except no backup DR (backup DIS) Sample lab diagram: NOTE. It is essential to understand that the IS-IS connectivity between areas relays on the level-1-2 adjacencies.  Concepts and Operations:  - Router is an Intermediate System and host is End System - SNPA - Subnetwork Point of Attachment - concept that relates to data link/data switch - Frame is Data Link PDU / Packet is Network PDU - LSP - Link State PDU - LSP is a pack...

grep basics grep is a command line tool for searching plain text to match a regular expression grep use examples: #grep 'import' test_requests.py - will display line in the file that contains word 'import' output:      f rom turtle import title      import requests      from bs4 import BeautifulSoup #grep -R 'import' . - will look for all files within the directory and subdirectories that contain word 'import ' output:      ./test_urllib:import urllib3      ./xml2-to-dict.py:import xmltodict      ./xml-to-dict.py:import xmltodict      ./eveng-request.py:import requests      ./parse_yaml.py:import yaml      ./test_requests.py:from turtle import title      ./test_requests.py:import requests      ./test_requests.py:from bs4 import BeautifulSoup      ./automate-l1.py:from __future__ import print_fun...

- YANG is defined in RFC 6020  - defines hierarhy of data, structures data models in to modules and submodules - used to model data for NETCONF - permits the definition of reusable groupings of nodes - RFC 6021 - describes common YANG types used in networking     these can be imported with import statment:        import "ietf-yang-types" {       prefix-yang;    }     - then as a reference when accessing definitions use "yang" as a prefix i.e.:     type yang:port-number      - Four types of nodes are used for data modeling:    a) Leaf node(s) - smallest component, one value i.e. ipv4 address     b) Leaf-list - a sequence of leaf nodes with exactly one value of a    particular type per leaf    c) Container nodes - group related nodes in a subtree    d) List nodes - defines a sequence of list entries - examples of build-in YANG data...

  BASH basics - acronym for "Bourne Again Shell" - allows for command and script processing - supports piping i.e.: $env | more  will add page breaks when displaying the information: - For help  "man" can be used to access detailed information about command i.e.: $man pwd will return: - sample commands: pwd - print current working directory ls - list files and directories, optionally can be used with "-a" (show all including hidden files) or "-l" to list permissions and user/group ownership, example: mkdir - create directory rm - deletes file or directory, useful flag " -rf " to force remove all files within deleted         folder cp - copy file or folder, does not delete the source file mv - move file/folder between directories, also can be used to rename files/folders         using  " mv -f " will force overwrite if destination file already exists cat - can be used to view or create files,...