1. Routing Protocols
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2. Objectives
• Understand basic concepts of routing.
• Explain the difference between routed protocols and
routing protocols.
• Configure IP routing in a large network.
• Understand different types of routing protocols.
• Understand interior and exterior routing protocols.
• Understand and configure RIP and IGRP.
• Understand how to verify IP routing.
• Explain EIGRP, OSPF, VLSM, and VPN.
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3. Routing
Routing is the act of moving information across an
internetwork from a source to a destination.
Routers don’t care about hosts – they only care about
networks and the best path to each network.
• Destination address
• Neighbor routers from which it can learn about remote
networks
• Possible routes to all remote networks
• The best route to each remote network
• How to maintain and verify routing information
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4. IP Routing in a Large Network
Router configuration is a fairly simple process, since you just
need to add IP addresses to your interfaces and then
perform a no shutdown on the interfaces.
2621A Configuration
To configure the 2621A router, you just need to add an IP
address to interface FastEthernet 0/0.
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5. IP Routing in a Large Network contd..
2501A Configuration
To configure 2501A, two interfaces need to be configured:
Ethernet 0 and Serial 0.
2501B Configuration
The configuration of 2501B is more of the same, except that
you also need to add the clock rate command to the data
communication equipment (DCE) interfaces connected to
both serial interfaces.
2501C Configuration
The configuration of 2501C is the same as 2501A except
that it has different network lDs.
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6. Configure IP Routing
The different types of routing are as follows:
• Static Routing
• Default Routing
• Dynamic Routing
Static Routing
Static routing protocols are hardly protocols at all. Before
routing begins, the network administrator establishes static
routing table mappings.
static routing systems are generally considered unsuitable
for today's large, constantly changing networks.
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7. Configure IP Routing contd..
Default Routing
We use default routing to send packets with a remote
destination network not in the routing table to the next-hop
router.
To configure a default route, you use wildcards in the
network address and mask locations of a static route.
Dynamic Routing
Dynamic routing protocols adjust to changing network
circumstances.
They do this by analyzing incoming routing update
messages.
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8. Routing Protocols
Routing is the process of determining where to send data
packets destined for addresses outside the local network.
Routing protocols allow a router to create and maintain
routing tables dynamically and to adjust to network
changes as they occur.
Types of Routing Protocols
• Distance Vector
• Link State
• Hybrid
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9. Routing Components
Routing involves two basic activities:
determining optimal routing paths and transporting
information groups (typically called packets) through an
internetwork .
Path Determination
Routing protocols use metrics to evaluate what path will be
the best for a packet to travel.
To aid the process of path determination, routing algorithms
initialize and maintain routing tables, which contain route
information.
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10. Router for Inter-VLAN Communication
Network devices in different VLANs cannot communicate
with one another without a router to route traffic between
the VLANs.
In an IPX network, each VLAN is mapped to an IPX network
number.
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11. Interior Routing Protocols
An interior protocol is a routing protocol used inside -
interior to - an independent network system.
Exterior Routing Protocols
Exterior routing protocols are used to exchange routing
information between autonomous systems.
Moving routing information into and out of these monoliths
is the function of exterior routing protocols. Exterior routing
protocols are also called exterior gateway protocols.
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12. Routing Information Protocol (RIP)
The RIP, as it is more commonly called, is one of the most
enduring of all routing protocols. It is a true distance-vector
routing protocol.
Routing Updates
RIP sends routing-update messages at regular intervals and
when the network topology changes.
RIP routers maintain only the best route (the route with the
lowest metric value) to a destination.
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13. Routing Information Protocol (RIP) contd..
RIP Routing Metric
RIP uses a single routing metric (hop count) to measure the
distance between the source and a destination network.
RIP Stability Features
RIP prevents routing loops from continuing indefinitely by
implementing a limit on the number of hops allowed in a path
from the source to a destination.
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14. Routing Information Protocol (RIP) contd..
RIP Timers
RIP uses three different kinds of timers to regulate its
performance:
• Route update timer
• Route invalid timer
• Route flush timer
Packet Formats
There are 2 packet formats:
• RIP Packet Format
• RIP 2 Packet Format
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15. Routing Information Protocol (RIP) contd..
Configure RIP
To configure RIP routing, just turn on the protocol with the
router rip command and tell the RIP routing protocol which
networks to advertise.
Verifying the RIP Routing Tables
Each routing table should now have the routers’ directly
connected routes as well as RIP-injected routes received
from neighbor routers.
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16. Interior Gateway Routing Protocol
(IGRP)
The IGRP is a routing protocol that was developed in the
mid-1980s by Cisco Systems, Inc.
Cisco's principal goal in creating IGRP was to provide a
robust protocol for routing within an autonomous system
(AS).
IGRP Protocol Characteristics
IGRP is a distance vector Interior Gateway Protocol (IGP).
Distance vector routing protocols mathematically compare
routes using some measurement of distance.
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17. Interior Gateway Routing Protocol (IGRP) contd..
Timers
IGRP maintains a number of timers and variables containing
time intervals. These include an update timer, an invalid
timer, a hold-time period, and a flush timer.
Configuring IGRP Routing
The command used to configure IGRP is the same as the
one used to configure RIP routing with one important
difference – you use an autonomous System (AS) number.
Verifying the IGRP Routing Tables
Once the routers are configured, you need to verify the
configuration with the show ip route command.
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18. Verify IP Routing
The following list includes the commands you can use to
verify the routed and routing protocols configured on your
Cisco routers:
• show ip route
• show protocols
• show ip procotol
• debug ip rip
• debug ip igrp events
• debug ip igrp transactions
The Show Protocols Command
The show protocols command is useful because it displays
all the routed protocols and the interfaces on which the
protocol is enabled.
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19. Verify IP Routing contd..
The Show IP Protocol Command
The show ip protocol command shows you the routing
protocols that are configured on your router.
The Debug IP RIP Command
The debug ip rip command sends routing updates as they
are sent and received on the router to the console session.
The Debug IP IGRP Command
With the debug ip igrp command, there are two options,
events and transactions.
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20. Enhanced Interior Gateway Routing
Protocol (EIGRP)
EIGRP is an enhanced version of IGRP. In a well designed
network, EIGRP scales well and provides extremely quick
convergence times with minimal network traffic.
Basic Theory
A typical distance vector protocol saves the following
information when computing the best path to a destination.
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21. Enhanced Interior Gateway Routing Protocol (EIGRP) contd..
Configuration
It is recommended that you configure all routers on a
network segment with primary IP addresses on the same
subnet .
Verify
This section provides information you can use to confirm
your configuration is working properly
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22. Open Shortest Path First (OSPF)
OSPF is an Interior Gateway Protocol (IGP) developed by
the OSPF working group of the Internet Engineering Task
Force (IETF).
Configure with IP Addresses
On point-to-point links such as High-Level Data Link Control
(HDLC) and PPP, Open Shortest Path First (OSPF) runs as
a point-to-point network type.
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23. Variable-Length Subnet Mask (VLSM)
The ability to specify a different subnet mask for the same
network number on different subnets is called VLSM.
RIPv1 and IGRP are classful protocols and are incapable
of carrying subnet mask information in their updates.
Virtual Private Networks (VPN)
One of the most popular approaches to establishing a
secure computing and network environment is the virtual
private network (VPN).
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