In this presentation, we are comparing the two most commonly used routing protocols in the world: BGP and OSPF. we discuss their similarities and differences

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BGP vs OSPF
Mikrotik User Meeting Manila,
January 16, 2018
Achmad Mardiansyah
achmad@glcnetworks.com
GLC Networks, Indonesia

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Agenda
● Introduction
● Routing review
● BGP vs OSPF
● Q & A
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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: webinar (every 2 weeks, see our schedule on website)
●
●
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About me
● Name: Achmad Mardiansyah
● Base: bandung, Indonesia
● Linux user since 1999, mikrotik user since 2007,
● Mikrotik Certified Trainer
(MTCNA/RE/WE/UME/INE/TCE/IPv6)
● Mikrotik Certified Consultant
● Teacher at Telkom University (Bandung, Indonesia)
● Website contributor: achmadjournal.com,
mikrotik.tips, asysadmin.tips
● More info:
http://au.linkedin.com/in/achmadmardiansyah
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Past experiences
● 2017, Libya (north africa): remote wireless migration
for a new Wireless ISP
● 2016, United Kingdom: conducting a workshop for
wireless ISP, migrating a bridged to routed network
● 2015, West Borneo: supporting wireless
infrastructure project
● 2014, Senegal (west africa): TAC2 engineer for HLR
migration from NOKIA to ERICSSON
● 2013, Malaysia: setup a wireless communication to
support an international event
● 2012, Dompetdhuafa Indonesia: optimising indoor
wireless infrastructure

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About Telkom University
● Located in Bandung, Indonesia
● 7 Faculties, 27 schools
● Areas: Engineering, Communications, Computing, Bussiness and
management, Arts
● 650+ Academic staff, 400+ Administration staff, 20000+ students
● An exchange program
● Runs mikrotik academy program
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Mikrotik academy @ TEL-U
● Started in 2013
● Embedded into schools curricula
● 100% hands-on
● Get MTCNA certification
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Mikrotik in Indonesia
● Very popular product for networking
● Early adopters (beginning of 2000)
● Many schools already join Mikrotik
Academy programs
● Lots of training classes
● Biggest MUM in the world (2500+
participants, 2-day event)
● Very active community (facebook, telegram,
forum, etc)
● What..? you don't know Mikrotik? Where
have you been?
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Routing (review)
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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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● 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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● 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
2222
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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BGP vs OSPF
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Working layer
BGP
● On layer 5, need to establish session
between router. Aka. peer
● On layer 4, TCP port 179
OSPF
● No dedicated session peer between router
● Working on layer 3 (network layer),
multicast
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AS1
Inter-AS vs intra-AS
BGP
● Mainly for inter-AS routing exchange
● Can be used also for intra-AS
OSPF
● Mainly used for intra-AS routing exchange
●
2525
AS4
AS3
AS2

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AS1
iBGP vs eBGP
BGP
● eBGP: inter-AS
● iBGP: intra-AS
OSPF
● Used in conjunction with iBGP
●
2626
AS4
AS3
AS2

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Routing perspective
BGP
● See the whole AS number as a single unit,
no matter how many routers in it
OSPF
● See each router as single unit
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R2
R1
R2
R1

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Path determination
BGP
● Based on AS path
OSPF
● Based on cost, calculated per link
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R2
R1
R2
R1

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Building routing table (topology)
BGP
● Only exchange information to peer
OSPF
● Information is flooded to all routers. Each
router understand the whole topology
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R1 R1

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BGP
● eBGP. scope=40, target-scope=10
● iBGP. scope=40, target-scope=30
Scope and target scope
OSPF
● scope=20, target-scope=10
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AS1
3030
AS4
AS3
AS2
R1
Indirect gateway
for R1

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BGP
● Only one routing entry is chosen
● Doesnt support ECMP
Load balancing (outgoing traffic)
OSPF
● Applied on 2 or more links with equal cost.
● Use ECMP method
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R1 R1
R2R2

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QA
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End of slides
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