The document outlines the GLC Networks webinar on Internet Protocol, led by trainer Achmad Mardiansyah, covering topics such as OSI layers, IP addressing, routing, and troubleshooting techniques. Key aspects include a review of prerequisite knowledge, introduction to GLC Networks and its offerings, as well as a live practice session. Participants are encouraged to engage in Q&A and share their experiences during the webinar.

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Internet Protocol
Deep dive
GLC Webinar,
24 Feb 2022
Achmad Mardiansyah
achmad@glcnetworks.com
GLC Networks, Indonesia

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Agenda
● Introduction
● Review prerequisite knowledge
● Internet Protocol
● Troubleshooting
● Live practice
● Q & A
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Introduction
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What is GLC?
● Garda Lintas Cakrawala (www.glcnetworks.com)
● Based in Bandung, Indonesia
● Areas: Training, IT Consulting
● Certified partner for: Mikrotik, Ubiquity, Linux foundation
● Product: GLC radius manager
● Regular event
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Trainer Introduction
● Name: Achmad Mardiansyah
● Base: bandung, Indonesia
● Linux user since 1999, mikrotik user since 2007, UBNT
2011
● Mikrotik Certified Trainer
(MTCNA/RE/WE/UME/INE/TCE/IPv6)
● Mikrotik/Linux Certified Consultant
● Website contributor: achmadjournal.com, mikrotik.tips,
asysadmin.tips
● More info: http://au.linkedin.com/in/achmadmardiansyah
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Past experience
● 2020-2022 (Congo DRC, PNG, Malaysia): network support,
radius/billing integration
● 2019, Congo (DRC): build a wireless ISP from ground-up
● 2018, Malaysia: network revamp, develop billing solution and
integration, setup dynamic routing
● 2017, Libya (north africa): remote wireless migration for a new
Wireless ISP
● 2016, United Kingdom: workshop for wireless ISP, migrating a
bridged to routed network
● 2015, Kalimantan, wireless support
● See our website for more details
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About GLC webinar?
● First webinar: january 1, 2010 (title: tahun baru
bersama solaris - new year with solaris OS)
● As a sharing event with various topics: linux,
networking, wireless, database, programming,
etc
● Regular schedule
● Irregular schedule: as needed
● Checking schedule:
http://www.glcnetworks.com/schedule
● You are invited to be a presenter
○ No need to be an expert
○ This is a forum for sharing: knowledge, experiences,
information
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Please introduce yourself
● Your name
● Your company/university?
● Your networking experience?
● Your mikrotik experience?
● Your expectation from this course?
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Prerequisite
● This presentation requires some prerequisite knowledge
● We assume you already know:
○ Computer network
○ Mikrotik RouterOS
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Review prerequisite knowledge
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7 OSI layer & protocol
● OSI layer Is a conceptual model from ISO (International
Standard Organization) for project OSI (Open System
Interconnection)
● When you send a message with a courier, you need to
add more info to get your message arrived at the
destination (This process is called encapsulation)
● What is protocol
○ Is a set of rules for communication
○ Available on each layer
● Communication consist of series encapsulation
○ SDU: service data unit (before PDU)
○ PDU: protocol data unit (after header is added)
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Layered model (TCP/IP vs ISO) and encapsulation
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/ datagram

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Layer 4 header
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Layer 3 header
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Layer 2 header, ethernet
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Layer 2 header, 802.11
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Did you notice?
● There is a big overhead on encapsulation process
● More encapsulation means less payload?
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IP spec
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IP spec (RFC 791)
● Defined long time ago (what 1981?)
● Defines how the IP header looks like
● Still used up to know
● New version -> IPv6
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IP: addressing
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Layer 2 vs Layer 3 addressing
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Layer 2 Layer 3
● Burned-in address
● Adjacent communication
● Consist of 48 bit binary, written in
HEX format. 1 HEX = 4 bit
● Unique for every physical port
● 6 first HEX digit -> represent the
manufacturer
● Logical address
● End-to-end communication
● IPv4 32 bit long
● 2 versions: IPv4 (our focus) and IPv6
● Consist of network part & host part
● Can be class based IP address
(without subnet)
● Now it is classless IP address ->
VLSM (variable length subnet mask)
● CIDR (classless inter domain routing)

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Addressing, IANA, RIR
● Internet is based on IP (internet protocol)
addressing scheme -> RFC791
● Addressing has to be unique.
● We need an international body that regulates IP
addressing -> IANA (Internet Assigned Number
Authority)
● IANA delegates (some of its authority) to RIR
“Regional Internet Registry”
● RIR delegates to country’s
● Every organisation must have IP address block to
join the internet and build a routing scheme
among their equipment
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How the layer 3 address look like?
● IPv4 address is 32 bit long
● Written in binary -> always think in binary
● Displayed to human in decimal every 8 bit (octet).
● Has 2 parts: network part and host part
● Like a phone number 0812 XXXXXXXX -> hierarchical
● All devices in the network will have same network part
● First and last address cannot be used (for network id and broadcast id)
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Network part host part

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Physical connection (physical topology)
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R2
R1
R3
● Router connects layer 2 segments
● Router works on layer 3
● Meaning, each layer 2 segment has
network ID

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Logical connection (logical topology) and routing table
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Routing table:
● A table at router that is used to forward packet
● Available on every devices (router and host)
● Entry is executed sequentially
192.168.0.0/26
R1
192.168.0.1/26
192.168.0.3/26
192.168.0.2/26
R3
R2
192.168.1.0/24
192.168.2.0/24
192.168.3.0/24
192.168.3.3/24
192.168.3.9/24
192.168.2.9/24
192.168.2.2/24
192.168.1.1/24
192.168.1.9/24
destination gateway
192.168.0.0/26 direct
192.168.1.0/24 direct
192.168.2.0/24 192.168.0.2
192.168.3.0/24 192.168.0.3
192.168.16.3/32 192.168.0.2
0.0.0.0/0 (default gw) 192.168.0.3

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We need IP address planning
● Chopping a big network into smaller subnets
● Aggregate small subnets into bigger range
● make sure no ip addresses are overlap
● Dont use excel please… :-(
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Forwarding packets using routing table
● It works like a firewall: match and action
● When a packet arrived, routing table is used to forward packets
● You should think in binary to understand how it works
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destination gateway
192.168.16.3/32
11000000 10101000 00001000 00000011
192.168.0.2
192.168.0.0/26
11000000 10101000 00000000 00
direct
192.168.1.0/24
11000000 10101000 00000001
direct
192.168.2.0/24
11000000 10101000 00000010
192.168.0.2
192.168.3.0/24
11000000 10101000 00000011
192.168.0.3
0.0.0.0/0
(no match)
192.168.0.3

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A packet arrived at R1… (example)
Destination IP address of the packet is 192.168.2.6, which gateway do we use?
A: 192.168.2.6 = (11000000 10101000 00000010 00000110)
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destination gateway
192.168.16.3/32
11000000 10101000 00001000 00000011
192.168.0.2
192.168.0.0/26
11000000 10101000 00000000 00
direct
192.168.1.0/24
11000000 10101000 00000001
direct
192.168.2.0/24
11000000 10101000 00000010
192.168.0.2
192.168.3.0/24
11000000 10101000 00000011
192.168.0.3
0.0.0.0/0 192.168.0.3

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Where routing table lookup happens?
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Administrative distance (analogy)
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CITY 1 100 km
CITY 2 120 km
CITY 2 90 km
CITY 3 500 km
CITY 4 250 km
10.10.10.0/24 192.168.0.1 10
10.10.20.0/24 192.168.0.2 12
10.10.20.0/24 192.168.0.3 9
10.10.30.0/24 192.168.0.3 50
10.10.40.0/24 192.168.0.4 25

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Administrative distance
● Distance is considered when prefix length is
same
● Lowest distance wins
● Administrative distance policy is depends on
vendor
● Table on the right shows an example of
administrative distance on cisco router
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IP: routing
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VLSM RFC
● Variable-Length Subnet Masking (VLSM)
● Can divide an IP address block into subnets
of different sizes using / (slash) notation
● Solution the in efficient of classful IP address
(fixed length). No more class A, B, C
● RFC: 1878 (1895)
● Basis for CIDR
● Example: 23.45.0.0/17
○ 23.45.0.0/25
○ 23.45.0.128/25
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CIDR RFC
● CIDR: Classless Inter-Domain Routing
● Provides a new and more flexible way to specify network
addresses in routers (using slash as notation)
● allow flexible allocation of Internet Protocol (IP) addresses.
● CIDR lets a routing table entry represent an aggregation of
networks that exist in the forward path
● Each IP address has a network prefix that identifies their
network
● RFC: 1519
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Router and Routing
● Router is a network device that is used to forward packets, based on layer 3
information (layer 3 header)
● Routing is the process of selecting a path for traffic in a network, or between
or across multiple networks
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Physical
router
Router
icon

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Static routing
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● Entries on routing table is created manually
● Admin must manage routing table in all
routers
● Admin have full control
192.168.0.0/26
R1
192.168.0.1/26
192.168.0.3/26
192.168.0.2/26
R3
R2
192.168.1.0/24
192.168.2.0/24
192.168.3.0/24
192.168.3.3/24
192.168.3.9/24
192.168.2.9/24
192.168.2.2/24
192.168.1.1/24
192.168.1.9/24
destination gateway
192.168.0.0/26 direct
192.168.1.0/24 direct
192.168.2.0/24 192.168.0.2
192.168.3.0/24 192.168.0.3
192.168.16.3/32 192.168.0.2
0.0.0.0/0 192.168.0.3

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Dynamic routing
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● Router will talk to each other with routing protocol
(RIP, OSPF, BGP)
● Entries on routing table is created automatically
● Admin must have a good knowledge about routing
protocol
192.168.0.0/26
R1
192.168.0.1/26
192.168.0.3/26
192.168.0.2/26
R3
R2
192.168.1.0/24
192.168.2.0/24
192.168.3.0/24
192.168.3.3/24
192.168.3.9/24
192.168.2.9/24
192.168.2.2/24
192.168.1.1/24
192.168.1.9/24
destination gateway
192.168.0.0/26 direct
192.168.1.0/24 direct
192.168.2.0/24 192.168.0.2
192.168.3.0/24 192.168.0.3
192.168.16.3/32 192.168.0.2
0.0.0.0/0 192.168.0.3

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Routing is one-way
● Currently, routing is done one-way only
● Forwarding process on router is based on destination IP address
● There is no guarantee incoming path is similar to outgoing path
● We can only control outgoing forwarding
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R1
192.168.0.1/26
192.168.0.3/26 R3
R2
192.168.1.0/24
192.168.2.0/24
192.168.3.0/24
192.168.3.3/24
192.168.3.9/24
192.168.2.9/24
192.168.2.2/24
192.168.1.1/24
192.168.1.9/24

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Autonomous system (AS)
● Is a collection of routers and networks under one administration and apply
single routing policy
● AS is identified by a number (ASN), given by RIR (Regional Internet Registry:
APNIC, ARIN, RIPE, etc)
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AS1
AS4
AS3
AS2

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Interior vs exterior routing
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IGP vs EGP
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AS1
IGP: Interior Gateway Protocols
● Routing protocol that runs internally within AS
(intra-AS)
● Connecting networks within AS
● Example: RIP, OSPF
EGP: Exterior Gateway Protocol
● Routing protocol that runs between AS
● Connecting an AS to other ASes
● Example: BGP
AS4
AS3
AS2

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Multiple routing protocol: scope and target scope
● Route scope and target scope attributes can be used to resolve nexthop
router.
● Normally nexthops can be resolved only through routes that are on link.
● It is very useful when the gateway is not directly connected
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AS1
R1
AS3
AS2
Indirect
gateway R1

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IP troubleshooting
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Troubleshooting layer 3
● Always starts from lowest layer.
○ Make sure layer 1 and 2 are OK
● Reachability test: ping
● Path analysis: traceroute
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Live practice
● SSH client
● SSH parameters
○ SSH address
○ SSH port
○ SSH username
○ SSH password
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QnA
Any questions?
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Interested? Just come to our training...
● Topics are arranged in systematic and
logical way
● You will learn from experienced teacher
● Not only learn the materials, but also
sharing experiences, best-practices, and
networking
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End of slides
● Thank you for your attention
● Please submit your feedback: http://bit.ly/glcfeedback
● Find our further event on our website :
https://www.glcnetworks.com
● Like our facebook page:
https://www.facebook.com/glcnetworks
● Slide: https://www.slideshare.net/glcnetworks/
● Discord (bahasa indonesia):
(https://discord.gg/6MZ3KUHHBX )
● Recording (youtube):
https://www.youtube.com/c/GLCNetworks
● Stay tune with our schedule
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