Routing
Routing is the process of moving data
from one network to another by
forwarding packets via gateways.
Path Determination Graphic
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Protocols
Routing
protocols
IGP
LSP
DVP
Routed
protocols
EGP
Hybrid
IP
IPX
BGP
RIP
RIPV2
IGRP
OSPF
IS-IS
EIRG
P
APPLE
TALK
Autonomous System
An Autonomous System (AS) is a group of IP networks, which
has a single and clearly defined external routing policy.
EGP
Exterior Gateway
Protocols are used
for routing between
Autonomous Systems
AS 1000
AS 3000
IGP
AS 2000
Interior Gateway Protocols are
used for routing decisions
within an Autonomous System.
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Fig. 48 IGP and EGP (TI1332EU02TI_0004 The Network Layer, 67)
Interior Gateway Protocol
(IGP)
Exterior Gateway
Protocol (EGP)
Interior Gateway Protocol
(IGP)
AS 1000
AS 3000
EGP
EGP
IGP
EGP
AS 2000
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Fig. 49 The use of IGP and EGP protocols (TI1332EU02TI_0004 The Network Layer, 67)
IGP and EGP
An autonomous system is a network or set of networks under
common administrative control, such as the cisco.com domain.
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Types of Protocols
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ROUTED PROTOCOLS are nothing more
than data being transported across the
networks. Routed protocols include:
•
Internet Protocol
– Telnet
– Remote Procedure Call (RPC)
(Client is requesting for the services
from the server)
– SNMP (simple network
management protocol)
SNMP use, one or more administrative
computers have the task of monitoring or
managing a group of hosts or devices on a
computer network
– SMTP
•
Novell IPX
NetWare is a network operating system (NOS) that
provides transparent remote file access and numerous
other distributed network services, including printer
sharing and support for various applications such as
electronic mail transfer and database access.
•
ROUTING PROTOCOLS are the software that
allow routers to dynamically advertise and
learn routes, determine which routes are
available and which are the most efficient
routes to a destination. Routing protocols used
by the Internet Protocol suite include:
•
Routing Information Protocol (RIP and RIP II)
•
Open Shortest Path First (OSPF)
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Intermediate System to Intermediate System
(IS-IS)
Interior Gateway Routing Protocol (IGRP)
•
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Cisco's Enhanced Interior Gateway Routing
Protocol (EIGRP)
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Border Gateway Protocol (BGP)
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Appletalk
AppleTalk is a proprietary suite of protocols
developed by Apple Inc. for networking
computers
Banyan Vines
(for Virtual Integrated NEtwork Service) was a
computer network operating system and the set
of computer network protocols it used to talk to
client machines on the network. The Banyan
company based the VINES operating system on
Unix
Routing Protocol
Router
Switch
Router
Router
Router
Switch
Router
What is
an optimal
route ?
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Routing Protocols
Routing protocols
includes the following:
processes for sharing
route information
allows routers to
communicate with
other routers to update
and maintain the
routing tables
Examples of routing
protocols that support
the IP routed protocol
are:
RIP, IGRP,
OSPF, BGP,
and EIGRP.
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Routed Protocols
Protocols used at the network layer that transfer data from one host to another across
a router are called routed or routable protocols. The Internet Protocol (IP) and Novell's
Internetwork Packet Exchange (IPX) are examples of routed protocols. Routers use
routing protocols to exchange routing tables and share routing information. In other
words, routing protocols enable routers to route routed protocols.
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Types of Routing
• Static Routing
• Default Routing
• Dynamic Routing
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Static Routing
• It is configured by Administrator manually.
• Mandatory need of Destination Network ID
• It is Secure & fast
• Used for Small organizations with a network of 10-15 Routers.
• Administrative distance for Static Route is 0 and 1.
It is the “trustworthiness” of the routing information. Lesser the
Administrative distance, higher the preference.
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Disadvantages of Static Routing
• Administrative work is more.
• Compulsory need of Destination Network ID’s
• Used for only Small organizations
• It cannot dynamically update topology changes.
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Default Routing
• A Default routing protocol is configured for unknown
destinations.
• Generally used in the internet where the destinations are
unknown.
Example : The address of yahoo is unknown.
• Configured at end points
• It is the last preferred routing
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Default Routing - Real Time Example
INTERNET
HYD
E0
192.168.1.150/24
E0
202.54.30.150/24
LAN - 192.168.1.0/24
IP 202.54.30.1/24
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Dynamic Routing
Advantages of Dynamic over static :
• There is no need to know the destination networks.
•
Need to advertise the directly connected networks.
•
Updates the topology changes dynamically.
•
Administrative work is reduced
•
Used for large organizations.
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Types of Dynamic Routing Protocols
• Distance Vector Protocol
• Link State Protocol
• Hybrid Protocol
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Distance Vector Protocol
• Works with Bellman Ford algorithm
• Periodic updates
• Classful routing protocol
• Full Routing tables are exchanged
• Updates are through broadcast
• Also known as “Routing By Rumor”
• Example: RIP, IGRP
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Link State Protocol
• Works with Dijkstra algorithm
• Link state updates
• Classless routing protocol
• Missing routes are exchanged
• Updates are through multicast
• Also known as “ Routing by Intelligence”
• Example : OSPF, IS-IS
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Hybrid Protocol
• Works with DUAL algorithm
• Link state updates
• Classless routing protocol
• Missing routes are exchanged
• Updates are through multicast
• Also known as “ Routing by Intelligence”
• Example : EIGRP
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Routing Information Protocol
• Open Standard Protocol
• Classful routing protocol
• Updates are broadcasted via 255.255.255.255
• Administrative distance is 120
• Metric : Hop count
Max Hop counts : 15
Max routers : 16
• Load Balancing of 4 equal paths
• Used for small organizations
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Rip Timers
• Update timer : 30 sec
– Time between consecutive updates
• Invalid timer : 180 sec
– Time a router waits to hear updates
– The route is marked unreachable if there is no update
during this interval.
• Flush timer : 240 sec
– Time before the invalid route is purged from the routing
table
• Holddown timer : 180sec
– Specifies the amount of time for which the information
about poorer routes are ignored.
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RIP Timers
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Update Timer: 30 sec.
Time between consecutive updates.
Invalid Timer: 180 sec
It is a time a router waits to hear updates
The route is marked unreachable if there is no update during this
interval
Flush Timer: 240 sec
Time before the invalid route is purged from the routing table.
Hold down Timer: 180 sec
Specifies the amount of time for which the information about
poorer router is ignored.
Disadvantages of RIP
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•
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More bandwidth utilization since it sends updates for every 30
secs.
Doesn’t consider bandwidth, works only with hop count.
Slow convergence.
Formation of routing loops.
Note: The biggest disadvantage of RIP is, it sends updates every
30 sec i.e., bandwidth consumption.
RIP Version 2 Features and Concepts
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Supported in IOS version 11.1 and later
Route updates include subnet masks
Supports Variable-Length Subnet Masks (VLSM)
Authentication of Routing Updates
Next hop address carried with each Routing Update
Multicast address used for Routing Updates
Same as RIP Version 1
Exception is the Multicasting of Routing updates to a
Multicast address of 224.0.0.9.
• RIP Version 2 Features and Concepts
• Supported in IOS version 11.1 and later
•
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Route updates include subnet masks
Supports Variable-Length Subnet Masks (VLSM)
Authentication of Routing Updates
Next hop address carried with each Routing Update
Multicast address used for Routing Updates
Same as RIP Version 1
Exception is the Multicasting of Routing updates to a
Multicast address of 224.0.0.9.
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Distance Vector
Uses Autonomous Systems
Update Timers = 90 sec
Default maximum hop Count = 100,
configurable to a maximum of 255.
Holddown timers = 3 x 90 sec + 10
Invalidation Timer = 3 x 90 sec = 270 sec
Random Jitter = 20% (72-90 sec)
Metrics used : BDRLM. By Default it only uses