2. Outline
• Overview
• Routing Overview
• Static and Dynamic Route Comparison
• Static Route Configuration
• Default Route Forwarding Configuration
• Static Route Configuration Verification
• Dynamic Routing Protocol Overview
• Features of Dynamic Routing Protocols
• The ip classless Command
• InterVLAN Routing
• Summary
3. To route, a router needs to do the following:
• Know the destination address
• Identify the sources from which the router can learn
• Discover possible routes to the intended destination
• Select the best route
• Maintain and verify routing information
Router Operations
4. • Routers must learn destinations that are
not directly connected.
• Routers must learn destinations that are
not directly connected.
Router Operations (Cont.)
5. Static Route
• Uses a route that a
network administrator
enters into the router
manually
Dynamic Route
• Uses a route that a network
routing protocol adjusts
automatically for topology
or traffic changes
Identifying Static and Dynamic Routes
6. Static Routes
• Configure unidirectional static routes to and from
a stub network to allow communications to occur.
• Configure unidirectional static routes to and from
a stub network to allow communications to occur.
7. • Defines a path to an IP destination network or subnet or host
Router(config)# ip route network [mask]
{address | interface}[distance] [permanent]
Static Route Configuration
8. Static Route Example
• This is a unidirectional route. You must have a route
configured in the opposite direction.
9. Default Routes
• This route allows the stub network to reach all known
networks beyond Router A.
• This route allows the stub network to reach all known
networks beyond Router A.
10. Verifying the Static
Route Configuration
Router# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
U - per-user static route
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
10.0.0.0/8 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Serial0
S* 0.0.0.0/0 is directly connected, Serial0
11. • Routing protocols are
used between routers to
determine paths and maintain
routing tables.
• After the path is determined, a
router can route a routed
protocol.
What Is a Routing Protocol?
12. • An autonomous system is a collection of networks
under a common administrative domain.
• IGPs operate within an autonomous system.
• EGPs connect different autonomous systems.
Autonomous Systems: Interior or Exterior
Routing Protocols
14. Classes of Routing Protocols
Distance vector Routing protocols
The Distance vector protocols find the best path
to the destination by judging the Distance to that
hop. [ each time a packet goes to a router is
known as HOP]
Any route with the Least hops will be the Best
route.
Distance vector Routing protocols
The Distance vector protocols find the best path
to the destination by judging the Distance to that
hop. [ each time a packet goes to a router is
known as HOP]
Any route with the Least hops will be the Best
route.
15. • Routers pass periodic copies of their routing table to neighboring
routers and accumulate distance vectors.
Distance Vector Routing Protocols
16. • Routers discover the best path to destinations from each neighbor.
Sources of Information and Discovering
Routes
18. • Updates proceed step by step from router to router.
Maintaining Routing Information
19. Link state routing protocols
The protocols which choose SHORTEST PATH to
determine the best path for the Destination.
These protocols maintain three types of Tables.
1.For directly attached neighbors.
2.For determining the Topology of whole inter-
network.
3.Routing table.
Link state routing protocols know more about the
Internetwork then any other type of protocol.
OSPF is the complete link state protocol.
Link state protocols send regular updates about
there routing table to all the connected neighbors
after a regular interval.
20. Link state routing protocols.
The protocols which use features of both
Distance Vector and Link state are known as hybrid
protocols.
Exa.. EIGRP
Distance vector + link state
21. ROUTING LOOPS
Distance vector routing protocols keep track of any
changes that occur in the internetwork by
broadcasting the periodic routing table updates out
to all Routers connected. This is good for the
maintenance of the internetwork but not for the
processing of the routers processor. But the
routing updates are send after a specific time
period.
An inconsistent routing tables updates can
cause ROUTING LOOPS
22. ROUTING LOOPS
Suppose we have the above scenario with 6
networks. And the update period will be 30
seconds.
Suppose we have the above scenario with 6
networks. And the update period will be 30
seconds.
23. ROUTING LOOPS
If network 6 fails then router E will send the update to
router C because all other router have the route to
network six from the router C.
Now router C know about the Failure of the Network 6
but all other A,B and D are still don`t know about the
failure bcz C didn`t send update to them till now.
So they keep on sending the routing updates to C for
the network 6. and they assume that YES they have
path for network 6.
If network 6 fails then router E will send the update to
router C because all other router have the route to
network six from the router C.
Now router C know about the Failure of the Network 6
but all other A,B and D are still don`t know about the
failure bcz C didn`t send update to them till now.
So they keep on sending the routing updates to C for
the network 6. and they assume that YES they have
path for network 6.
24. ROUTING LOOPS
After some time when router C will send update to
router B.it will stop routing for network 6.
BUT router A & D are still unknown about the failure
{not updated} and they send a update to router B that
they have still path for network 6.
After some time when router C will send update to
router B.it will stop routing for network 6.
BUT router A & D are still unknown about the failure
{not updated} and they send a update to router B that
they have still path for network 6.
25. ROUTING LOOPS
The problem occur when before update to router A & D
about the failure the router A send a HELLO update
packet to router B & D about the network 6. and router B
& D think that network six will be reachable through
router A. and they start sending update to all of the router
about this update.
Then router A send request for N/W 6 to B & D, D will
send to B, B will send to A, and again and again they will
repeat the same procedure in a LOOP.
Known as routing loop.
26. Metrics or Solutions to stop the Routing
loops
Maximum HOP CountMaximum HOP Count
One way of solving the loops is to define the
maximum hop count RIP permits a hop count of 15
only means if anything that requires 16th
hop is
deemed as unreachable.
Means after a loop of 15 hops the next network
will be considered as unreachable
27. Metrics or Solutions to stop the Routing
loops. Cont..
Split Horizon
In this methodology the routing information cant be
sent back to the direction from which it was received
In this methodology the routing information cant be
sent back to the direction from which it was received
28. Metrics or Solutions to stop the Routing
loops. Cont..
Flush Updates/ Trigger Updates
It means when the is a change in any
internetwork topology a special update is sent to
all neighbors immediately so that they can
update there routing tables.
29. Metrics or Solutions to stop the Routing
loops. Cont..
Route Poisoning
If there any network will down then corresponding
router will start advertising that network as a 16th
network or unreachable network.
This will stop all other to send packets for that
network
30. Collision Domain
It is a network segment with multiple hosts in
which they all shares the same bandwidth.
Exa.. HUB
Hub is a 1 collision and 1 broadcast domain
Means if two hosts transmits at same time a
collision can occur
Means if two hosts transmits at same time a
collision can occur
31. Broadcast domain
The boundary in which all devices can see and
participate in the broadcast sent from the nay node to
any node in the network.
A broadcast domain is always created by the routers.
32. Device Specifications
HUB:- 1 Collision domain
1 Broadcast domain
At a time only one request can travel to all the nodes
connected with the hub.
And if there is any collision then a single collision can
stop whole network
Switch:- 1 Broadcast domain, multiple collision domain,
each port is a separate collision domain, multiple unicast
domain.
A Switch always performs 1st
time broadcast when it is
power ON and after that it will always use unicast
method for data distribution
33. Device Specifications conti…
Router:- each port of a router is a separate collision
domain and a broadcast domain.
Bcz any broadcast or any collision in the
internetwork will only affects the connected port of
the router not to all the interfaces of the router.
A router used to handle all its ports separately.
34. Administrative Distance:
Ranking Routes
It is used to give the rank to the routing protocols
It is an integer from 0-255
It will show the trustworthiness of any routing
protocol.
0 means most trusted.
255 means traffic can`t be pass to that route.
35. Administrative Distance:
Ranking Routes
How the AD is used……………………………………….
Whenever a router will receive two routing updates
At same time then it will check for the AD distance
for that updates and save the update with least AD
in its routing table.
BUT if the both have the same AD then it will follow
the routing metrics of protocol that is used for the
routing from the side of routing update.
Like [hop count/shortest path]
How the AD is used……………………………………….
Whenever a router will receive two routing updates
At same time then it will check for the AD distance
for that updates and save the update with least AD
in its routing table.
BUT if the both have the same AD then it will follow
the routing metrics of protocol that is used for the
routing from the side of routing update.
Like [hop count/shortest path]
36. Administrative Distance:
Ranking Routes
Source AD
Connected 0
Static 1
RIP 120
IGRP 100
EIGRP 90
OSPF 110
Unknown 255
255 will never
be used.
Source AD
Connected 0
Static 1
RIP 120
IGRP 100
EIGRP 90
OSPF 110
Unknown 255
255 will never
be used.
37. Classfull Routing Overview/ subnetting
FLSM
• Classfull routing protocols do not include the subnet mask
with the route advertisement.
• Within the same network, consistency of the subnet masks is
assumed.
• Summary routes are exchanged between foreign networks.
• These are examples of classfull routing protocols:
– RIP version 1 (RIPv1)
– IGRP
38. Classless Routing Overview/ Subnetting
VLSM
• Classless routing protocols include the subnet mask with the
route advertisement.
• Classless routing protocols support variable-length subnet
mask (VLSM).
• Summary routes can be manually controlled within the
network.
• These are examples of classless routing protocols:
– RIP version 2 (RIPv2)
– EIGRP
– OSPF
– IS-IS
40. Summary
• Routing is the process by which items get from one location to
another. In networking, a router is the device used to route
traffic. Routers can forward packets over static routes or
dynamic routes, based on the router configuration.
• Static routers use a route that a network administrator enters
into the router manually. Dynamic routes use a router that a
network routing protocol adjusts automatically for topology or
traffic changes.
• Unidirectional static routes must be configured to and from a
stub network to allow communications to occur.
• The ip route command can be used to configure default route
forwarding.
• The show ip route command is used to verify that static routing
is properly configured. Static routes are signified in the
command output by “S.”
41. Summary (Cont.)
• Dynamic routing protocols determine how updates are
conveyed, what knowledge is conveyed, when to convey
knowledge, and how to locate recipients of the updates.
• A routing protocol that has a lower administrative value is
more trustworthy than a protocol that has a higher
administrative value.
• There are three classes of routing protocols: distance vector,
link-state, and balanced hybrid.
• The ip classless command can be used to prevent a router
from dropping a packet that is destined for an unknown
subnetwork of a directly attached network if a default route
is configured.
Notes de l'éditeur
Slide 1 of 2
Purpose: This slide states the chapter objectives.
Emphasize: Read or state each objective so that each student has a clear understanding of the chapter objectives.
Note: Catalyst switches have different CLIs. The Catalyst 2900xl and the Catalyst 1900 has a Cisco IOS CLI. The Cisco IOS CLI commands available on the 2900xl is different from the 1900. The Catalyst 5000 family has no Cisco IOS CLI, and use the set commands instead. This class only covers the configuration on the Catalyst 1900 switch.
Slide 1 of 2
Purpose: This figure introduces students to routing. The router must accomplish the items listed in the figure for routing to occur.
Emphasize: Path determination occurs at Layer 3, the network layer. The path determination function enables a router to evaluate the available paths to a destination and to establish the best path.
Routing services use network topology information when evaluating network paths. This information can be configured by the network administrator (static routes) or collected through dynamic processes (routing protocols) running in the network.
Transition: How do you represent the path to the packet’s destination?
Slide 2 of 2
Purpose: This figure explains that routers must learn about paths that are not directly connected.
Emphasize: The router already knows about directly connected networks. It must learn about those networks that are not connected. This chapter describes how routers learn about those paths.
Purpose: This figure introduces students to static and dynamic routes.
Emphasize: Static knowledge is administered manually—a network administrator enters it into the router’s configuration. The administrator must manually update this static route entry whenever an internetwork topology change requires an update. Static knowledge can be private—by default it is not conveyed to other routers as part of an update process. You can, however, configure the router to share this knowledge.
Dynamic knowledge works differently. After the network administrator enters configuration commands to start dynamic routing, route knowledge is updated automatically by a routing process. Whenever new topology information is received from the internetwork, routers update neighbors about the route change.
Purpose: This figure describes how a static route operates.
Emphasize: For intercommunication, static routes must be configured in both directions. Static routes are often used to route traffic to a stub network or other network where only a single route to that network exists.
Purpose: This figure describes the command syntax used to establish an IP static route.
Emphasize: A static route allows manual configuration of the routing table. No dynamic changes to this table entry will occur as long as the path is active. Routing updates are not sent on a link that is only defined by a static route; hence, conserving bandwidth.
The ip route field descriptions are as follows:
network—Destination network or subnet
mask—Subnet mask
address—IP address of next-hop router
interface—Name of the interface to use to get to the destination network
Transition: The next figure provides a static route configuration example.
Purpose: This figure gives an example of a static route configuration.
Purpose: This figure gives an example of a default route configuration.
Emphasize: With an address and subnet mask of 0.0.0.0 0.0.0.0 in the ip route statement, packets for any network not listed in the routing table will be sent to the next hop, 172.16.2.2.
Slide 2 of 6
Purpose: This figure shows how the show frame-relay LMI command is used to verify the LMI type used for signaling.
Emphasize: Describe the highlighted output to the students.
Purpose: This figure introduces students to routing protocols and compares routing protocols to routed protocols.
Emphasize: If network 10.120.2.0 wants to know about network 172.16.2.0, it must learn it from its S0 (or possibly S1) interface.
Note: The two routing protocols that will be taught in this course are RIP and IGRP. They are both distance vector routing protocols.
Purpose: This figure discusses autonomous systems, IGPs and EGPs.
Emphasize: Introduce the interior/exterior distinctions for routing protocols, as follows:
Interior routing protocols are used within a single autonomous system
Exterior routing protocols are used to communicate between autonomous systems
The design criteria for an interior routing protocol require it to find the best path through the network. In other words, the metric and how that metric is used is the most important element in an interior routing protocol.
Exterior protocols are used to exchange routing information between networks that do not share a common administration. IP exterior gateway protocols require the following three sets of information before routing can begin:
A list of neighbor (or peer) routers or access servers with which to exchange routing information
A list of networks to advertise as directly reachable
The autonomous system number of the local router
Purpose: This figure introduces the three classes of routing protocols.
Emphasize: There is no single best routing protocol.
Note: Distance vector routing protocol operation is covered in detail later in this course. Link state and hybrid are only briefly explained after the distance vector discussion. Refer students to the ACRC to learn more about link-state and hybrid routing protocols.
Purpose: This figure introduces the three classes of routing protocols.
Emphasize: There is no single best routing protocol.
Note: Distance vector routing protocol operation is covered in detail later in this course. Link state and hybrid are only briefly explained after the distance vector discussion. Refer students to the ACRC to learn more about link-state and hybrid routing protocols.
Purpose: This figure introduces the distance vector routing algorithm, the first of the classes of routing protocols, and outlines how it operates.
Emphasize: Distance vector algorithms do not allow a router to know the exact topology of an internetwork.
This information is somewhat analogous to the information found on signs at a highway intersection. A sign points toward a road leading away from the intersection and indicates the distance to the destination.
Further down the highway, another sign also points toward the destination, but now the distance to the destination is shorter.
As long as each successive point on the path shows that the distance to the destination is successively shorter, the traffic is following the best path.
Layer 3 of 3
Emphasize: Layer 3 adds the final entries received some time later that have distances of 2 from routers A and C.
Emphasize: How the routing algorithm defines “best” determines the most important characteristics of each routing algorithm.
Hop count—Some routing protocols use hop count as their metric. Hop count refers to the number of routers a packet must go through to reach a destination. The lower the hop count, the better the path. Path length is used to indicate the sum of the hops to a destination. As indicated in the figure, RIP uses hop count for its metric.
Ticks—Metric used with Novell IPX to reflect delay. Each tick is 1/18th of a second.
Cost—Factor used by some routing protocols to determine the best path to a destination; the lower the cost, the better the path. Path cost is the sum of the costs associated with each link to a destination.
Bandwidth—Although bandwidth is the rating of a link’s maximum throughput, routing through links with greater bandwidth does not always provide the best routes. For example, if a high-speed link is busy, sending a packet through a slower link might be faster. As indicated in the figure with highlighting, delay and bandwidth comprise the default metric for IGRP.
Delay—Depends on many factors, including the bandwidth of network links, the length of queues at each router in the path, network congestion on links, and the physical distance to be traveled. A conglomeration of variables that change with internetwork conditions, delay is a common and useful metric. As indicated in the figure with highlighting, delay and bandwidth comprise the default metric for IGRP.
Load—Dynamic factor can be based on a variety of measures, including CPU use and packets processed per second. Monitoring these parameters on a continual basis can itself be resource intensive.
Layer 3 of 3
Layer 3 adds router B, which receives the updated routing table from router A. In turn, router B will perform its own process to update its routing table given this new topology update from router A.
Distance vector updates occur step by step.
Typically, a router sends updates by multicasting its table on each configured port, but other methods, such as sending the table only to preconfigured neighbors, are employed by some routing algorithms.
Multicast is used by the RIP2, OSPF, and EIGRP routing protocols. RIP and IGRP use broadcast.
The routing table can be sent routinely and periodically, or whenever a change in the topology is discovered. Updates sent when changes occur are called triggered updates.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This figure introduces administrative distance.
Emphasize: An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. In a large network, some routing protocols and some routers can be more reliable than others as sources of routing information.
The default administrative distance for static routes and various routing protocols is listed in the Student Guide. The lower the distance, the more trustworthy the route is. For example, in the figure, the packet would learn the route learned via IGRP.
Purpose: This slide discuss the initial configurations on the routers and switches.
Note: There is no setup mode on the Catalyst 1900 switch.