Download Routed protocols

Cisco 2 - Routers
Chapter 4
Module 6
Routing & Routing
Protocols
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Cisco 2 - Routers
Routing Protocols
Chapter 4
Important function of a router (layer 3 device):
• Examine incoming data packets & make path selection
based on:
• information stored in its routing tables
Router evaluates the available paths to a destination &
establishes the best path for routing a packet.
Most routing protocols use the shortest & best path - but each
use different methods.
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Cisco 2 - Routers
The Routing Process
192.168.1.56
01-00-A5-C3-26-6B
Chapter 4
• The protocol
address (IP) always
remains the same.
192.168.1.56
34-7E-33-12-C9-20
192.168.1.56
6A-5F-0D-09-8B-AA
192.168.1.56
BC-48-03-8F-FF-AA
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• The physical
address (MAC)
changes at each
hop.
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Cisco 2 - Routers
Static Routing
Chapter 4
Characteristics of static routes:
• administrators establish static routing table
maps
• routes do not change, unless changed by an
administrator
• used in environments where network traffic is
predicable & network design is simple
• can’t react quickly to network changes; hence
are considered unsuitable for today’s LANs
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Static Routing
Cisco 2 - Routers
Chapter 4
Static route can be defined in global config mode:
RouterA(config)# ip route <dest network> <subnet mask> < interface | next hop>
192.16.10.1
s0
Network 200.10.10.0
Router A
Router B
RouterA(config)# ip route 200.10.10.0 255.255.255.0 192.16.10.1
RouterA(config)# ip route 200.10.10.0 255.255.255.0 s0
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Cisco 2 - Routers
s0
Static Routing
Chapter 4
192.16.10.1
Network 200.10.10.0
Router A
Router B
e0
195.10.10.0 net
The command for a static address from 195.10.10.0 to get to network
200.10.10.0 is:
RouterA(config)# ip route 200.10.10.0 255.255.255.0 192.16.10.1
RouterA(config)# ip route 200.10.10.0 255.255.255.0 s0
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Static Routing
Cisco 2 - Routers
s0
Chapter 4
192.16.10.1
Network 200.10.10.0
Router A
Router B
RouterA(config)# ip route 200.10.10.0 255.255.255.0 192.16.10.1
In the routing table, the above example will have an administrative
distance of 1.
RouterA(config)# ip route 200.10.10.0 255.255.255.0 s0
In the routing table, the above example will have an administrative
distance of 0.
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Static Routing
Cisco 2 - Routers
s0
Chapter 4
192.16.10.1
Network 200.10.10.0
Router A
Router B
RouterA(config)# ip route 200.10.10.0 255.255.255.0 192.16.10.1
If the network 192.16.10.0 goes down for any reason, the static
address on RouterA will be removed from the routing table.
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Cisco 2 - Routers
Default Static Route (Gateway of Last Resort)
Chapter 4
If router doesn’t know where to send a packet, it can use a default route:
RouterA(config)# ip route 0.0.0.0 0.0.0.0 < interface | next hop>
192.16.10.1
s0
Router A
Internet
RouterA(config)# ip route 0.0.0.0 0.0.0.0 192.16.10.1
RouterA(config)# ip route 0.0.0.0 0.0.0.0 s0
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Default/Static Route
Cisco 2 - Routers
Chapter 4
Verify a static route or default route with the commands:
show running-config
(s run)
Or
show ip route
(s ip route)
Test a static route or default route with the commands:
ping
Or
traceroute
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Chapter 4
Configuring Static Routes
with Outgoing Interface
Cisco 2 - Routers
Outgoing
interface
Administrative
distance of 0
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Cisco 2 - Routers
Chapter 4
Configuring Static Routes
with Next-hop IP Address
Next hop
interface
Administrative
distance of 1 default
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Cisco 2 - Routers
Routed vs. Routing Protocols
Chapter 4
Routed vs. Routing:
Routed protocols are protocols that are moved over
a network. (PCs use routed protocols to talk to each other.)
• TCP/IP
• IPX
• Apple Talk …
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Cisco 2 - Routers
Routed vs. Routing Protocols
Chapter 4
Routed vs. Routing:
Routing protocols route routed protocols through a network.
(Routers use routing protocols to talk to each other about networks &
paths.)
• RIP (Routing Information Protocol) -- RIP Ver2
• IGRP (Interior Gateway Routing Protocol)
• EIGRP ( Enhanced IGRP)
• BGP (Border Gateway Protocol)
• OSPF (Open Shortest Path First)
• APPN (Advanced Peer-to-Peer Networking)
• IS-IS (Intermediate System-to Intermediate System)
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Cisco 2 - Routers
Autonomous Systems
Chapter 4
An autonomous system (AS) is a collection of networks
under a common administration.
The American Registry of Internet Numbers (ARIN)
assigns an identifying number to each AS.
AS is a 16 bit number.
Some routing protocols such as IGRP, EIGRP requires
AS.
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Cisco 2 - Routers
Routing Protocols
Chapter 4
When all routers in an internetwork are operating with
the same knowledge of the routes available in a
network it is said to have converged.
Fast convergence is desirable because it reduces the
period of time in which routers would continue to make
incorrect routing decisions.
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Cisco 2 - Routers
Chapter 4
Routing protocols are divided into 2 classes:
Interior and Exterior
• interior - used for routing information within
networks that are under a common network
administrator
• RIP
• IGRP
• OSPF
• EIGRP
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Cisco 2 - Routers
Chapter 4
Routing protocols are divided into 2 classes:
Interior and Exterior
Exterior - used for routing information between
networks that do not share a common
administrator.
• EGP (exterior gateway protocol)
• BGP (border gateway protocol)
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Cisco 2 - Routers
Classes of Routing Protocols
Chapter 4
Classes of Routing Protocols
• distance-vector - determines the direction &
distance
• IGRP
• RIP
• link-state (also called shortest path first) recreates the exact topology of the entire network).
• OSPF
• IS-IS
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Cisco 2 - Routers
Distance Vector Routing Protocols
Chapter 4
Distance vector routing algorithms pass periodically
copies of a routing table from router to router. These
regular updates are based on the routing algorithm
know as Bellman-Ford algorithm.
However a distance vector algorithms do not allow a
router to know the exact topology of an internetwork as
each router only sees its neighbor routers.
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Cisco 2 - Routers
Link-state Routing Protocol
Chapter 4
Link-state algorithms are also known as Dijkstras algorithm or SPF
(shortest path first) algorithm.
Link-state routing algorithms maintain a complex database of
topology information. It maintains full knowledge of distant routers
and how they are interconnected.
Link-state routing uses:
• Link-state Advertisements (LSAs)
Small packets of routing info that are sent between routers
• SPF algorithm (shortest path first)
• Topological database
• Routing tables
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Cisco 2 - Routers
Link-state Routing Protocol
Chapter 4
Link-state makes an update only when there is a
topology change.
Link-state concerns itself with minimizing:
• processor overhead
• memory requirements
• bandwidth consumption
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Cisco 2 - Routers
RIP routing protocol
Chapter 4
Characteristics of RIP are:
• distance vector
• metric is hop count
• if the hop count is greater than 15, the packet is
discarded
• table is updated every 30 seconds
Each router that a message has to go through to get to
its destination is considered one hop count. If the
message pass through 2 routers the hop count is 2.
If the destination is the next router, then the hop count
is 0.
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Cisco 2 - Routers
IGRP Routing Protocol
Chapter 4
IGRP:
• must be assigned an AS (autonomous system number - 16 bit number)
• Cisco proprietary
• distance-vector
• metrics
• delay
• bandwidth (1200 bps - 10 Gbps)
• reliability (1-224) (higher the number, more reliable)
• load (1-244) (higher the number, the more load carried)
•sends updates every 90 seconds
• maximum hop count is 255 (default 100)
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Cisco 2 - Routers
OSPF Routing Protocol
Chapter 4
Characteristics of OSPF:
• link-state routing protocol
• open standard
• uses the SPF algorithm to calculate the lowest
cost to a destination
• routing updates are flooded as topology changes
occur.
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Cisco 2 - Routers
EIGRP Routing Protocol
Chapter 4
Characteristics of EIGRP are:
• distance-vector
• Cisco proprietary
• uses load balancing
•uses a combination of distance vector & link-state
features
• use Diffused Update Algorithm (DUAL) to
calculate the shortest path
• updates broadcast every 90 seconds
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Cisco 2 - Routers
BGP Routing Protocol
Chapter 4
Characteristics of BGP are:
• distance vector exterior routing protocol
• used between ISP and clients
• used to route internet traffic between AS
(autonomous systems)
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Cisco 2 - Routers
Configure routing protocols
Chapter 4
RouterA#config t
RouterA(config)# router <routing protocol> [AS number]
RouterA(config-router)# network <networks on the routers interfaces>
As an example:
RouterA(config)# router rip
RouterA(config-router)# network 192.16.10.0
As an example:
RouterA(config)# router igrp 100
RouterA(config-router)# network 192.16.10.0
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Cisco 2 - Routers
Configure routing protocols
Chapter 4
210.45.20.0 net
s0
s1
192.10.10.0 net
Router A
e0
172.120.0.0 net
RouterA# config t
RouterA(config)# router rip
RouterA(config-router)# network 192.10.10.0
RouterA(config-router)# network 172.120.0.0
RouterA(config-router)# network 210.45.20.0
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Cisco 2 - Routers
Border Gateways & Autonomous Systems
Chapter 4
Autonomous systems have an identifying number, which is assigned
to it by the American Registry of Internet Numbers (ARIN) or a
provider. This autonomous system number is a 16-bit number.
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Cisco 2 - Routers
Chapter 4
Module 6
Routing & Routing
Protocols
END
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