This document provides an overview of routing protocols and concepts: - It defines what a route is and explains that routing protocols are used to exchange route information between routers to direct packet flow. - Key concepts covered include the routing table, static and dynamic routes, classification of routing protocols by area and algorithm, and route metrics. - It also discusses routing protocol preference, equal cost multi-path routing, and the longest prefix match method used to select routes.

1. Routing Protocol Basis
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2. Route technology is the key point that
internet is running continuously.
Route is a very interesting and complex
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Route is a very interesting and complex
task, and eternal topic.

3. Upon completion of this course, you will be
able to :
Know the concept of route
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Know the classification of routing
protocol
Understand the routing process of data
packet in the network
Understand the structure of routing table

4. What’s The Route?
A route is the path information to guide IP packets to be
transferred.
Destination
network N
E0/1
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Other networks
E0/0 S0/0
E0/1
RTA
RTB
RTC

5. The Key Function of routing
Check the destination of the data packet
Confirm the information resource
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Discover possible route
Select best route
Validate and maintain route information

6. Routing Table Establishment
E0/0
E1/0
10.1.1.0
192.168.2.0
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protocol destination interface
DIRECT 10.1.1.0 E0/0
OSPF 192.168.2.0 E1/0

7. Routes—Discovered by Data Link Layer
[RTB]display ip routing-table
Routing Tables: Public
Destinations : 8 Routes : 8
Destination/Mask Proto Pre Cost NextHop Interface
10.1.1.0/30
RTA
10.1.2.0/24
.1
.1 .2
.2
RTB
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Destination/Mask Proto Pre Cost NextHop Interface
10.1.1.0/30 Direct 0 0 10.1.1.1 Serial0/0/0
10.1.1.1/32 Direct 0 0 127.0.0.1 InLoopBack0
……
10.1.2.1/32 Direct 0 0 127.0.0.1 InLoopBack0
10.1.2.2/32 Direct 0 0 10.1.2.2 Serial0/0/1
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoopBack0
RTC

8. Routes—Static Route
[RTA] display ip routing-table
Routing Tables: Public
RTB
2.2.2.2/32
10.1.1.0/30
RTA
.1 .2
Configure static route towards
destination network 2.2.2.2/32
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Routing Tables: Public
Destinations : 8 Routes : 8
Destination/Mask Proto Pre Cost NextHop Interface
2.2.2.2/32 Static 60 0 10.1.2.2 Ethernet0
10.1.1.0/30 Direct 0 0 10.1.1.1 Serial0
10.1.1.1/32 Direct 0 0 127.0.0.1 InLoopBack0
10.1.1.2/32 Direct 0 0 10.1.1.2 Serial0
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoopBack0

9. Routes—Discovered by Dynamic Routing
Protocol
[RTB]display ip routing-table
Routing Tables: Public
10.1.2.0/24
.1
OSPF
RIP
RTA
RTC
172.16.1.1/32
.2
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Routing Tables: Public
Destinations : 10 Routes : 10
Destination/Mask Proto Pre Cost NextHop Interface
10.1.1.0/30 Direct 0 0 10.1.1.2 Serial0/0/0
10.1.1.1/32 Direct 0 0 10.1.1.1 Serial0/0/0
……
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoopBack0
172.16.1.1/32 OSPF 10 1563 10.1.2.2 Serial0/0/1
192.168.1.0/24 RIP 100 1 10.1.1.1 Serial0/0/0
10.1.1.0/8
RTB
.1
192.168.2.1/24
.2

10. Static and Dynamic Route
Static route Dynamic route
The route configured
manually by network
The route that router gets
from other routers via
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manually by network
administrator
When network topological
is changed, administrator
need to update static route
routing protocol
When network topological
is changed, routers will
update route information
automatically

11. Routing Protocol
Routing protocol is like language that used to exchange information between
routers, routers shares network status and network reachable information via
routing protocol.
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routing protocol.
The communication peers must run same protocols that used to exchange
routing information.
Routing protocol define a set of rules about communication between the routers
Routing protocol maintains routing table and provide the best forwarding path.

12. Routing Protocols Classification——Working
Area
IGPs：
：
：
：RIP OSPF ISIS
EGPs：
：
：
：BGP
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AS100 AS200

13. Routing Protocols Classification——Protocol
Algorithm
According to protocol algorithm
Distance-Vector routing protocol
− It includes RIP and BGP. Thereinto, BGP is also called
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− It includes RIP and BGP. Thereinto, BGP is also called
Path-Vector routing protocol.
Link-State routing protocol
− It is also called the shortest path first routing protocol,
includes OSPF and IS-IS.

14. Routing Protocols Classification——Service
Application
According to service application, routing protocol can be divide
into the following types:
Unicast Routing Protocol: includes RIP、OSPF、BGP and IS-
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Unicast Routing Protocol: includes RIP、OSPF、BGP and IS-
IS and so on.
Multicast Routing Protocol : includes DVMRP、PIM-SM、PIM-
DM and so on.

15. Routing Table
[Quidway] display ip routing-table
Routing Tables:
Destination/Mask proto pref Metric Nexthop Interface
0.0.0.0/0 Static 60 0 120.0.0.2 Serial0/0
8.0.0.0/8 RIP 100 3 120.0.0.2 Serial0/1
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8.0.0.0/8 RIP 100 3 120.0.0.2 Serial0/1
9.0.0.0/8 OSPF 10 50 20.0.0.2 Ethernet0/0
9.1.0.0/16 RIP 100 4 120.0.0.2 Serial0/0
11.0.0.0/8 Static 60 0 120.0.0.2 Serial0/1
20.0.0.0/8 Direct 0 0 20.0.0.1 Ethernet0/2
20.0.0.1/32 Direct 0 0 127.0.0.1 LoopBack0

16. Preference of Routing Protocol
If there are multiple routes, the route with higher preference (the
smaller value, the higher preference) will be used to guide IP packet
to be transferred.
RIP OSPF
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Routing table
10.0.0.0 R0
10.0.0.0 R1
10.0.0.0 R1

17. Preference of Routing Protocol
The default route preference on VRP platform is shown in the
following table
Routing protocol Preference
DIRECT 0
OSPF 10
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OSPF 10
IS-IS 15
STATIC 60
RIP 100
OSPF ASE 150
IBGP 255
EBGP 255
Untrustworthy 255

18. Route Metric
There are two routes from router A to D :
Path1： A→B→C→D ，the total route metric is 9
Path2： A→E→F→C→D ， the total route metric is 12
The router first selects the smaller metric route, and take it into the
routing table.
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2
5 2
6
3
1
A
B D
F
C
E
routing table.

19. Equal Cost Multi-Path (ECMP)
Equal Cost Multi-Path
There are several routes towards the same destination with same route
metric, if the route preference is same, these routes are all added into the
routing table, IP packet will be transferred over these link by turns.
Two equal cost multi-path from A to D:
A→B→C→D，total metric 5+5+8=18
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A→B→C→D，total metric 5+5+8=18
A→C→D， total metric 10+8=18
5
8
5
10
A
B
C D

20. Equal Cost Multi-Path
[RTB] display ip routing-table
Routing Tables: Public
Destinations : 13 Routes : 15
Destination/Mask Proto Pre Cost NextHop Interface
3.3.3.0/24 Direct 0 0 3.3.3.2 Serial2
3.3.3.1/32 Direct 0 0 3.3.3.1 Serial2
3.3.3.2/32 Direct 0 0 127.0.0.1 InLoopBack0
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10.1.1.1/32 Static 60 0 1.1.1.1 Serial0
Static 60 0 2.2.2.1 Serial1
Static 60 0 3.3.3.1 Serial2
20.1.1.1/32 Direct 0 0 127.0.0.1 InLoopBack0
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoopBack0
Equal Cost Multi-Path
realizes load-balance

21. The Longest Match
Destination makes
logical AND operation
Lookup routing table
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match
logical AND operation
with mask
Compare the destination
address in the routing table
Select the longest
matched route

22. The Example of Longest Match
[Quidway] display ip routing-table
Routing Tables:
Destination/Mask proto pref Metric Nexthop Interface
0.0.0.0/0 Static 60 0 120.0.0.2 Serial0/0
The data packet of destination 9.1.2.1 will match the route 9.1.0.0/16
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8.0.0.0/8 RIP 100 3 120.0.0.2 Serial0/1
9.0.0.0/8 OSPF 10 50 20.0.0.2 Ethernet0/0
9.1.0.0/16 RIP 100 4 120.0.0.2 Serial0/0
11.0.0.0/8 Static 60 0 120.0.0.2 Serial0/1
20.0.0.0/8 Direct 0 0 20.0.0.1 Ethernet0/2
20.0.0.1/32 Direct 0 0 127.0.0.1 LoopBack0

23. Thank You
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