Routing with a Distance
Vector Protocol in an
Enterprise Network
Introducing Routing and Switching in the Enterprise –
Chapter 5
Version 4.0
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Objectives

Compare and contrast a flat network and a
hierarchical routed topology.

Configure a network using RIP.

Describe and plan a network using EIGRP.

Design and configure a network using EIGRP.
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Critical Data
1. Crucial information and services typically reside near
the top of the hierarchy, in secured server farms or on
Storage Area Networks (SANs).
2. Communication between different levels of the
hierarchy requires a combination of LAN and WAN
technologies.
3. A star topology provides centralized control of the
network, but results in a single point of failure.
4. Mesh topologies eliminate the single point of failure,
but decentralize control and can increase cost.
5. A routing table is a data file that exists in RAM and
stores information about directly connected and
remote networks.
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Critical Data
6. A static route includes the network address and subnet mask
of the destination network, along with the exit interface or the
IP address of the next-hop router.
7. Dynamic routing protocols enable routers to share information
about the reachability and status of remote networks through
network discovery.
8. Limiting traffic to a single point of entrance or exit creates a
stub network.
9. In an enterprise network, static routes configured with exit
interfaces are ideal for point-to-point connections like those
between a border router and the ISP.
10. A special type of static route called a default route specifies a
gateway to use when the routing table does not contain a path
to a destination.
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Compare and Contrast a Flat Network
and a Hierarchical Routed Topology
 Enterprise hierarchy
 Combination of LAN and WAN technologies
 DMZ (e-commerce)
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Compare and Contrast a Flat Network and a
Hierarchical Routed Topology
Traffic control design
 Redundant links
 QoS
 Packet filtering
ROUTERS
• forward traffic and prevent
broadcasts from clogging the main
channels to crucial services
• control the flow of traffic between
LANs, allowing only the required
traffic to pass
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Compare and Contrast a Flat Network
and a Hierarchical Routed Topology
 Star and extended star topologies
provides centralized control of the network
scalable
 Mesh topologies
Partial mesh
Full mesh
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 Building the routing table
Exit interface or next hop
• associates each network with either an exit int or next hop
Administrative distance
•attaches a number to each route that represents the
trustworthiness or accuracy of the source of the routing
information
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 Directly connected routes - attaches to a router interface
 Static routes - manually configured
 Dynamic routes - share information about the
reachability and status of remote networks through
network discovery
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Exploration Exercise
 Packet Tracer 5.1.3.3
Connected
Static
Dynamic
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Compare and Contrast a Flat Network
and a Hierarchical Routed Topology
 Advantages of static routing
Stub networks
Security
Lower overhead
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Compare and Contrast a Flat Network and a
Hierarchical Routed Topology
 Static route configuration
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• Static routes configured with a next hop
interface require two steps to determine the
exit interface (recursive lookup)
• In a recursive lookup:
• The router matches the destination IP
address of a packet to the static route
• Matches the next hop IP address of the
static route to entries in its routing table
to determine which interface to use
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Compare and Contrast a Flat Network and a
Hierarchical Routed Topology
 Summary static routes
 Floating static routes
• Higher administrative distance than the route learned from a dynamic
routing protocol
• Does not display in the routing table unless dynamic fails
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 Default routes
specifies a gateway to use when the routing table does not
contain a path to a destination.
 Gateway of last resort
final default route, located on the border router, sends the traffic
to the ISP
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Routing Using the RIP Protocol
 Characteristics of distance vector protocols
share network information with directly connected neighbors - neighbor
routers then advertise the information to their neighbors
 Hop count metric
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Routing Using the RIP Protocol
 Characteristics of RIPv1
Automatically summarizes at classful boundary
Does not send subnet mask information in the update
Broadcasts routing updates every 30 seconds
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Routing Using the RIP Protocol
 Characteristics of RIPv1
• Does not support VLSM and CIDR
• A router configured with RIPv1 either uses the subnet mask
configured on a local interface, or applies the default subnet mask
• Due to this limitation, the subnets of the networks that RIPv1
advertises should not be discontiguous if correct routing is to occur.
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Routing Using the RIP Protocol
 RIPv2 configuration
• supports VLSM and CIDR
• subnet mask field is included in v2 updates (allows the use of
discontiguous networks)
• ability to turn off automatic summarization of routes
• multicasts its updates to 224.0.0.9
• has an authentication mechanism
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Routing Using the RIP Protocol
 RIPv2 shares many of the features found in RIPv1, such as:
 Hop-count metric
 15-hop maximum
 TTL equals 16 hops
 Default 30-second update interval
 Route poisoning, poisoned reverse, split horizon, and
holddowns to avoid loops
 Administrative distance of 120
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Routing Using the RIP Protocol
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Routing Using the RIP Protocol
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Routing Using the RIP Protocol
 RIPv2 configuration
Basic commands
Authentication
Default route redistribution
Lab 5.2.3.2
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Routing Using the RIP Protocol
Problems with RIP and their solutions:
Problem
Solution
• Discontiguous subnets
• No auto-summary
• Unnecessary traffic
• Passive-interface (disables
routing updates on specified
interfaces)
• Routing loops
• Poisoned reverse, split
horizon, holddown timer,
triggered updates
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Routing Using the RIP Protocol
Problems with RIP and their solutions:
• Poisoned reverse - sets the metric for
a route to 16, making it unreachable
• Split horizon - dictates that a router
receiving routing information on an
interface cannot send an update
about that same network back out the
same interface
• Holddown timer - refuses to accept
route updates with a higher metric to
the same destination network for a
period after a route goes down
• Triggered updates - when a route
fails, RIP does not wait for the next
periodic update
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Routing Using the RIP Protocol
 Verification commands
 Troubleshooting commands
 Ping for end-to-end connectivity
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Routing Using the RIP Protocol
 show ip protocols
 show ip route
 show ip rip database (Lists all the routes known by RIP)
 debug ip rip or debug ip rip {events} (Displays RIP
routing updates as sent and received in real time)
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Describe and Plan a Network Using
EIGRP
 Disadvantages of distance vector routing protocols
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Describe and Plan a Network Using EIGRP
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Describe and Plan a Network Using
EIGRP
 Compare EIGRP and RIP
• Instead of sending
periodic routing
updates, EIGRP
sends small hello
packets to maintain
knowledge of its
neighbors.
• EIGRP multicasts
partial updates
about specific
changes to only
those routers that
need the
information, not to all
routers in the area.
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Describe and Plan a Network Using
EIGRP
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Describe and Plan a Network Using
EIGRP
 Characteristics of EIGRP
Composite metric
Guaranteed loop-free operation
Bounded updates
Hello packets
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Describe and Plan a Network Using
EIGRP
 Activity 5.3.2.4
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Describe and Plan a Network Using EIGRP
 Neighbor table - lists information about directly connected
neighbor routers
 Topology table - lists all routes learned from each EIGRP
neighbor (successor and feasible – 5.3.3.2)
 Routing table - displays only the best paths called the
successor routes
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Describe and Plan a Network Using EIGRP
 Successors and feasible successors
 External routes
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Describe and Plan a Network Using EIGRP
 EIGRP neighbors and adjacencies
 Hello protocol - By default, hello packets are multicast every
5 seconds on links greater than a T1 and every 60 seconds
on T1 or slower links.
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Describe and Plan a Network Using EIGRP
 EIGRP packet types
• Whenever DUAL places a route in the active state, the router must
send a query packet to each neighbor.
• Neighbors must send replies, even if the reply states that no
information on the destination is available.
• The information contained in each reply packet helps DUAL to locate
a successor route to the destination network.
• Queries can be multicast or unicast.
• Replies are always unicast.
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Describe and Plan a Network Using EIGRP
 RTP: Reliable Transport Protocol - guarantees delivery
and receipt of EIGRP packets for all Network Layer
protocols
 PDM: Protocol Dependent Module - a router running IP,
IPX, and AppleTalk has three neighbor tables, three
topology tables, and three routing tables.
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Describe and Plan a Network Using
EIGRP
 EIGRP metrics and convergence – Bandwidth, Delay,
Reliability, Load
 K values
 Feasible and reported distance
• Feasible distance is the best
EIGRP metric along the path
to the destination from the
router.
• Advertised distance is the
best metric reported by a
neighbor.
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Activity 5.3.5.4
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Design and Configure a Network Using
EIGRP
 Basic EIGRP configuration
 Wildcard masks
 Logging neighbor changes
 Bandwidth
 Load balancing
NOTE: The AS number in
the command must match
on all routers that work
within the EIGRP routing
process.
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 EIGRP summarization
 Parent and child routes - The summary route is called the parent
route and the subnet routes are called the child routes.
 Null0 interface - Indicates that this is not an actual path, but a
summary for advertising purposes
 Manual summarization - no auto-summary
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Design and Configure a Network Using EIGRP
 Verification commands
 Troubleshooting commands
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EIGRP
 show ip protocols
Verifies that EIGRP is advertising the correct networks
Displays the autonomous system number and administrative
distance
 show ip route
Verifies that the EIGRP routes are in the routing table
Designates EIGRP routes with a D or a D EX
Has a default administrative distance of 90 for internal routes
 show ip eigrp neighbors detail
Verifies the adjacencies EIGRP forms
Displays the IP addresses and interfaces of neighbor routers
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EIGRP
 show ip eigrp topology
Displays successors and all feasible successors
Displays feasible distance and reported distance
 show ip eigrp interfaces detail
Verifies the interfaces using EIGRP
 show ip eigrp traffic
Displays the number and types of EIGRP packets sent and
received
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Design and Configure a Network Using EIGRP
 EIGRP issues and limitations
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Summary
 Enterprise networks are hierarchical
 Networks use static and dynamic routing to move
information
 Dynamic routing protocols are classified as either
distance vector or link state
 RIP is a distance vector routing protocol
 EIGRP is a Cisco proprietary distance vector routing
protocol with many advanced features
 EIGRP works best if its default features are modified to
suit the routing situation
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 Does not work in a multi-vendor environment because it
is a Cisco proprietary protocol
 Works best with a flat network design
 Must share the same autonomous system among
routers and cannot be subdivided into groups
 Can create very large routing tables, which requires
large update packets and large amounts of bandwidth
 Uses more memory and processor power than RIP
 Works inefficiently when left on the default settings
 Requires administrators with advanced technical
knowledge of the protocol and the network
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