This document provides an overview of a webinar discussing the Border Gateway Protocol (BGP) on RouterOS 7, led by trainers from GLC Networks. It covers the agenda, prerequisites, key concepts in networking including routing types, routing tables, and IP addressing, as well as specific details about BGP functionality, including its role in connecting autonomous systems. The content is geared toward sharing knowledge and experiences related to networking and BGP implementation.

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BGP on
RouterOS 7
GLC Webinar,
18 Jan 2022
Achmad Mardiansyah
M. Taufik nurhuda
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BORDER GATEWAY PROTOCOL

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Agenda
● Introduction
● Review prerequisite knowledge
● BGP
● BGP on ROS7
● 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
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● 2021 (PNG, Malaysia): network support, radius/billing
integration
● 2020 (Congo DRC, Malaysia): IOT integration,
network automation
● 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

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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 networking
○ Mikrotik administration
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Review prerequisite knowledge
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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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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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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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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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Typical connection (physical)
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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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Typical connection (logical) and routing table
Routing table:
● A table at router that is used to forward packet
● Available on every devices (router and host)
● Entry is executed sequentially
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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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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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Static routing
● Entries on routing table is created
manually
● Admin must manage routing table
in all routers
● Admin have full control
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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
● 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
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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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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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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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● 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
Important to note
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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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Interior vs exterior routing
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IGP and EGP
● IGP: Interior Gateway Protocols
○ Routing protocol that runs internally within 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
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AS1
IGP vs EGP
IGP
● intra-AS routing exchange
● Example: OSPF, RIP
EGP
● inter-AS routing exchange
● Can be used also for intra-AS
● Example: BGP
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AS4
AS3
AS2

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● 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
Multiple routing protocol: scope and target scope
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AS1
R1
AS3
AS2
Indirect
gateway R1

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How BGP works
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What is BGP features?
● Path Vector Protocol
● Incremental Updates
● Many options for policy enforcement
● Support VLSM
● Classless Inter Domain Routing (CIDR)
● Widely used for Internet backbone
● Connects Autonomous systems
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Path Vector Protocol
● BGP is classified as a path vector routing protocol (see RFC 1322)
● A path vector protocol defines a route as a pairing between a destination and
the attributes of the path to that destination.
● See AS path below
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Path vector protocol
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Image source: philip smith,
introduction to BGP

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BGP connectivity (aka. peering)
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source: philip smith,
introduction to BGP

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Building forwarding table for BGP
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source: philip smith,
introduction to BGP

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eBGP vs iBGP
● BGP is used
○ Internally, inside AS (iBGP - internal BGP)
○ Externally, between AS (eBGP - external BGP)
● iBGP is used to carry
○ Some/all Internet prefixes across ISP backbone
○ Prefixes from ISP customers
● eBGP is used to
○ Exchange prefixes with other ASes
○ Implement routing policy
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eBGP & iBGP
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source: philip smith,
introduction to BGP
IGP: interior Gateway Protocol.
E.g. RIP, OSPF, IEGRP

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External BGP Peering (eBGP)
● Between BGP speakers in different AS
● Should be directly connected
● Never run an IGP between eBGP peers
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source: philip smith,
introduction to BGP

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Internal BGP (iBGP)
● BGP peer within the same AS
● Not required to be directly connected
○ IGP takes care of inter-BGP speaker connectivity
● iBGP speakers must be fully meshed:
○ They originate connected networks
○ They pass on prefixes learned from outside the ASN
○ They do not pass on prefixes learned from other iBGP speakers
● Recommended to do peer with loopback interface
● To avoid mesh peering: AS confederation, route reflector
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source: philip smith,
introduction to BGP

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BGP connectivity
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Peering types
● Transit - service provided by an ISP to carry other ISP/customer traffic to
other network (internet). Usually is for commercial (paid service)
● Peering - 2 ISPs or more exchange traffic and routing information. Can be
commercial or non commercial (gratis). Example: peering on IXP (Internet
Exchange Point)
● Default - default route, sending traffic to default router of there is no explicit
match on routing table
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IP peering example
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IP transit example
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Border
router
Other
ISP
Other
ISP
Access
router
Access
router
Ordinary
customer
Customer
with AS
number
customer
Access network: GPON, WLAN,
FO, GSM, ethernet, etc
Clouds of
routers

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Peering and transit example (IIX vs openIXP?)
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source: philip smith,
introduction to BGP

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LIVE practice
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preparation
● SSH client
● SSH parameters
○ SSH address
○ SSH port
○ SSH username
○ SSH password
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Q & A
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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/en/
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● Discord (bahasa indonesia): (https://discord.gg/6MZ3KUHHBX)
● Recording (youtube): https://www.youtube.com/c/GLCNetworks
● Stay tune with our schedule
● Any questions?
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