1. Chapter 3 Routing Dynamically
CIS 82 Routing Protocols and Concepts
Rick Graziani
Cabrillo College
Version 6

2. Chapter 3 3.1 Dynamic Routing Protocols
3.2 Distance Vector Dynamic Routing
3.3 RIP and RIPng Routing
3.4 Link-State Dynamic Routing
3.5 The Routing Table
3.6 Summary

3. Chapter 3: Objectives
Explain the basic operation of dynamic routing protocols.
Compare and contrast dynamic and static routing.
Determine which networks are available during an initial network discovery phase.
Define the different categories of routing protocols.
Describe the process by which distance vector routing protocols learn about other networks.
Identify the types of distance-vector routing protocols.
Configure the RIP routing protocol.
Configure the RIPng routing protocol.
Explain the process by which link-state routing protocols learn about other networks.

4. Dynamic Routing Protocols

5. Types of Routing Protocols
Exterior Gateway Protocols
Interior Gateway Protocols
Distance Vector
Link State
Path Vector
Distance Vector Routing Protocols
Link State Routing Protocols
Path Vector
RIPv2
EIGRP
OSPFv2
IS-IS
BGP-4
RIPng
EIGRP for IPv6
OSPFv3 *
IS-IS for IPv6
BGP-4 for IPv6 or
MP-BGP
IPv4
IPv6
* OSPFv3 supports routing both IPv4 and IPv6.

6. Distance Vector Routing Protocol Operation
What does a street sign like this tell you?
How far (distance)
Which way (direction)
Distance vector
Routes are advertised as vectors of distance and direction.
Distance is defined in terms of a metric
Such as hop count
Direction is simply the:
Nexthop router or
Exit interface
Typically use the Bellman-Ford algorithm for the best-path (shortest) route determination

7. Distance Vector Routing Protocol Operation
Does not know the topology of an internetwork.
Only knows the routing information received from its neighbors.
Does not know if another path would actually be faster.
I don’t have a map of the network.
Would another path that is longer actually be faster? (speed limit)
All I know is how far and which direction (to next hop router)
Distance Vector routing protocols are like signposts along the path to the final destination.

8. Distance Vector Concepts

9. Distance Vector Routing Protocols
Routing Information Protocol (RIP)
Thee versions: IPv4 RIPv1 and RIPv2. RIPng for IPv6.
Uses hop counts as its metric.
Still around but don't use.
Interior Gateway Routing Protocol (IGRP)
Legacy Cisco Proprietary protocol.
Uses bandwidth and delay as its metric.
Enhanced IGRP (EIGRP)
Cisco Proprietary protocol.

10. Link-State Protocol Operation
Link-state routing protocol can create a “complete view,” or topology, of the network.
Link-state protocols are associated with Shortest Path First (SPF) calculations.
A link-state router uses the link-state information to:
Create a topology map
Select the best path to all destination networks in the topology.
Each router makes the decision! OR
Link State routing protocols is like having a complete map of the network topology

11. Link-State Protocol Operation
Link-state protocols work best in situations where
The network design is hierarchical, usually occurring in large networks.
The administrators have a good knowledge of the implemented link-state routing protocol.
Fast convergence of the network is crucial.

12. Link-State Routing Protocols
Open Shortest Path First (OSPF)
Popular standards based routing protocol
Intermediate System-to-Intermediate System (IS-IS)
Popular in provider networks

13. Link-State Concepts

14. Evolution of Dynamic Routing Protocols
Classful Routing Protocols
Classless Routing Protocols
BGP-MP &
OSPFv3
OSPFv2
RIPv2
RIPng
EGP
IGRP
RIPv1
IS-IS
EIGRP
BGP
IS-ISv6

15. Purpose of Dynamic Routing Protocols
Add dynamic routing protocol…
No changes!
The purpose of dynamic routing protocols includes:
Discovery of remote networks
Maintaining up-to-date routing information
Choosing the best path to destination networks
Ability to find a new best path if the current path is no longer available
Purpose of Dynamic Routing Protocols

16. Main Components of Routing Protocols
Data Structures
Neighbor table
Topology table
Neighbor table
Topology table
EIGRP Hello
EIGRP Update
Routing Protocol Messages
Algorithm
I will use the EIGRP DUAL algorithm to identify what the best routes are.
I will use the EIGRP DUAL algorithm to identify what the best routes are.
Purpose of Dynamic Routing Protocols (cont.)

17. Dynamic Routing Protocol Operation
Update
Update
Update
Update
Update
Update
In general, the operations of a dynamic routing protocol can be described as follows:
The router sends and receives routing messages on its interfaces.
The router shares routing messages and routing information with other routers that are using the same routing protocol.
Routers exchange routing information to learn about remote networks.
When a router detects a topology change the routing protocol can advertise this change to other routers.
Dynamic Routing Protocol Operation

18. Dynamic versus Static Routing

19. Using Static Routing
R2(config)# ip route
R1(config)# ip route
Static routing has several primary uses:
Best for smaller networks that are not expected to grow significantly.
Routing to and from a stub network.
A default route.
Networks typically use a combination of both static and dynamic routing.
Using Static Routing

20. Dynamic Routing Scenario
Dynamic routing is the best choice for large networks
Dynamic routing protocols help the network administrator manage the network:
Providing redundant paths
Automatically implementing the alternate path when a link goes down.
Media Description:
Based on the media from E
Networks often use both static and dynamic routing.

21. Reaching Remote Networks Dynamically
Hey I’m R1 and I’m using EIGRP to let my neighbors know that I’m directly connected to networks:
/24
/24
/30
Internet
Hey I’m R2 and I’m using EIGRP to let my neighbors know that I’m the gateway to the Internet (I have a default route to the Internet) and that I’m directly connected to:
/24
/24
/30
Media Description:
Use the media created for Routing

22. Routing Information Protocol (RIP)
Media Description:
Briefly describe the visual for this page.

23. Why RIP? RIP is rarely used in modern networks!
However, it’s useful as a foundation for understanding basic network routing.
This section provides a brief overview of how to configure basic RIP settings and to verify RIPv2.

24. RIP Cheat Sheet

25. RIP Reference Topology
/24
/24
/24 .1
G0/0 .1
DCE
DCE .1
S0/0/0
S0/0/0
S0/0/1
S0/0/1
G0/0 R1 R2 R3
G0/0 .1 .2 .2 .1
/30
/30
G0/0
Media Description:
Create as indicated.

26. Dynamic versus Static Routing Router RIP Configuration Mode
Use the router rip command to enable RIP v1
Use the no router rip command to disable RIP
3.2 – RIPv2
3.2.1 – Configuring the RIP Protocol
– Router RIP Configuration Mode

27. Configuring the RIP Protocol Advertise Networks
The network network-address router configuration mode command:
Enables RIP on all interfaces that belong to a specific network
Advertises the network in RIP routing updates sent to other routers every 30 seconds.
Note: RIPv1 is a classful routing protocol for IPv4.
Configuring the RIP Protocol Advertise Networks
3.2 – RIPv2
3.2.1 – Configuring the RIP Protocol
– Advertise Networks

28. Configuring the RIP Protocol Verify RIP Routing
show ip route – displays RIP routes installed in the routing table.
show ip protocols – displays IPv4 routing protocols configured on the router.
3.2 – RIPv2
3.2.1 – Configuring the RIP Protocol
– Verify RIP Routing

29. Configuring the RIP Protocol Enable and Verify RIPv2
Use the version 2 router configuration mode command to enable RIPv2
Use the show ip protocols command to verify that RIPv2 is configured.
Use the show ip route command to verify the RIPv2 routes in the routing table.
3.2 – RIPv2
3.2.1 – Configuring the RIP Protocol
– Enable and Verify RIPv2

30. Configuring the RIP Protocol Disable Auto Summarization
RIPv2 automatically summarizes networks at major network boundaries.
Use the no auto-summary router configuration mode command to disable auto summarization.
Use the show ip protocols command to verify that auto summarization is off.
3.2 – RIPv2
3.2.1 – Configuring the RIP Protocol
– Disable Auto Summarization

31. Configuring the RIP Protocol Configure Passive Interfaces
RIP updates:
Are forwarded out all RIP-enabled interfaces by default.
Only need to be sent out interfaces that are connected to other RIP-enabled routers.
Sending RIP updates to LANs wastes bandwidth, wastes resources, and is a security risk.
Use the passive-interface router configuration command to stop routing updates out the interface. Still allows that network to be advertised to other routers.
3.2 – RIPv2
3.2.1 – Configuring the RIP Protocol
– Configure Passive Interfaces

32. Configuring the RIP Protocol Propagate a Default Route
In the diagram a default static route to the Internet is configured on R1.
The default-information originate router configuration command instructs R1 to send the default static route information in the RIP updates.
3.2 – RIPv2
3.2.1 – Configuring the RIP Protocol
– Propagate a Default Route

34. RIP Passive Interfaces
/24
/24
/24 .1
G0/0 .1
DCE
DCE .1
S0/0/0
S0/0/0
S0/0/1
G0/0 R1 R2
S0/0/1 R3
G0/0 .1 .2 .2 .1
/30
/30
Sending out unneeded updates on a LAN:
Wastes Bandwidth 
Wastes Resources
Security Risk 
The passive-interface
Stops routing updates out the specified interface.
The network that the specified interface belongs to is still advertised in routing updates that are sent out other interfaces.
Should be configured on interfaces which do not connect to other RIP routers.

35. IPv4 Routing Table

36. Understanding the IPv4 Routing Table
For more details: Cisco IP Routing, by Alex Zinin (ISBN )

37. It is all because of classful IPv4 addressing

38. Back in the day…. When you got classful address, you got the whole thing
Class A /8
Class B
/16
Class C
/24
Class B
/16
Class C
/24
Class A /8
Class A /8
Class B
/16
Class C
/24

39. So, the IPv4 routing table is organized by classful addresses
R1#show ip route
S* /0 [1/0] via , Serial0/0/1
is directly connected, Serial0/0/1
/16 is variably subnetted, 5 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
R /24 [120/1] via , 00:00:12,Serial0/0/0
R /24 [120/2] via , 00:00:12,Serial0/0/0
R /28 [120/2] via , 00:00:12,Serial0/0/0
R /16 [120/2] via , 00:00:03, Serial0/0/0
/24 is variably subnetted, 5 subnets, 2 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R /30 [120/1]via ,0:0:12,Serial0/0/0
C /30 is directly connected, Serial0/0/1
L /30 is directly connected, Serial0/0/1
R1#

40. Level 1 route
A level 1 route is a route with a subnet mask equal to or less than the classful mask of the network address.

41. R1#show ip route
S* /0 [1/0] via , Serial0/0/1
is directly connected, Serial0/0/1
/16 is variably subnetted, 5 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
R /24 [120/1] via , 00:00:12,Serial0/0/0
R /24 [120/2] via , 00:00:12,Serial0/0/0
R /28 [120/2] via , 00:00:12,Serial0/0/0
R /16 [120/2] via , 00:00:03, Serial0/0/0
/24 is variably subnetted, 5 subnets, 2 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R /30 [120/1]via ,0:0:12,Serial0/0/0
C /30 is directly connected, Serial0/0/1
L /30 is directly connected, Serial0/0/1
R1#
Level 1 Ultimate route: a route with a subnet mask equal to or less than the classful mask of the network address.

42. Level 1 Parent route: A parent route is a heading:
R1#show ip route
S* /0 [1/0] via , Serial0/0/1
is directly connected, Serial0/0/1
/16 is variably subnetted, 5 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
R /24 [120/1] via , 00:00:12,Serial0/0/0
R /24 [120/2] via , 00:00:12,Serial0/0/0
R /28 [120/2] via , 00:00:12,Serial0/0/0
R /16 [120/2] via , 00:00:03, Serial0/0/0
/24 is variably subnetted, 5 subnets, 2 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R /30 [120/1]via ,0:0:12,Serial0/0/0
C /30 is directly connected, Serial0/0/1
L /30 is directly connected, Serial0/0/1
R1#
Level 1 Parent route: A parent route is a heading:
Indicates the presence of level 2 routes, also known as child routes.
Level 1 parent route is automatically created any time a subnet is added to the routing table.
A parent route is created whenever a route with a mask greater than the classful mask is entered into the routing table.

43. If Classful Parent matches, check Children for more specific match
If Classful Parent matches, check Children for more specific match. If no Children match look for a lesser match.
RTC# show ip route
Gateway of last resort is to network
R /24 [120/1] via , 00:00:02, Serial1
C /24 is directly connected, Serial1
C /24 is directly connected, Ethernet0
/24 is subnetted, 3 subnets
C is directly connected, Loopback2
C is directly connected, Loopback3
C is directly connected, Loopback1
S* /0 [1/0] via
RTC# ping
Sending 5, 100-byte ICMP Echoes to , timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5),round-trip min/avg/max=56/57/60 ms
Packet’s Destination IP Address:

44. Routing Table Lookup Process
IP Packet
Routing Table
Find “best match”
/prefix-length in the route indicates the number of bits that must match the destination IPv4 address for this route to be a match
When a router receives a packet on one of its interfaces.
The routing table lookup process compares the destination IP address of the incoming packet with the entries in the routing table.
The best match between the packet’s destination IP address and the route in the routing table is used to determine to which interface to forward the packet.

45. A packet is destined for 172.16.0.10
The router has three possible routes that match this packet:
/12
/18
/26
Of the three routes, /26 has the longest match and is therefore chosen to forward the packet.
Media Description:
Use the media from E

46. L 209.165.200.233/30 is directly connected, Serial0/0/1 R1#
R1#show ip route | begin Gateway
Gateway of last resort is to network
S* /0 [1/0] via , Serial0/0/1
is directly connected, Serial0/0/1
/16 is variably subnetted, 5 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
R /24 [120/1] via , 00:00:12,Serial0/0/0
R /24 [120/2] via , 00:00:12,Serial0/0/0
R /28 [120/2] via , 00:00:12,Serial0/0/0
R /16 [120/2] via , 00:00:03, Serial0/0/0
/24 is variably subnetted, 5 subnets, 2 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R /30 [120/1]via ,0:0:12,Serial0/0/0
C /30 is directly connected, Serial0/0/1
L /30 is directly connected, Serial0/0/1
R1#
Packet with Destination IPv4 address
One Level 1 Ultimate Routes to choose from.
/16 is the best (only) match, the longest match (coming).
Longest match: Most left-most bits that match between destination IP address and route in routing table
At a minimum it must match the number of bits in the route as indicated by the subnet mask.

47. L 209.165.200.233/30 is directly connected, Serial0/0/1 R1#
R1#show ip route | begin Gateway
Gateway of last resort is to network
S* /0 [1/0] via , Serial0/0/1
is directly connected, Serial0/0/1
/16 is variably subnetted, 5 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
R /24 [120/1] via , 00:00:12,Serial0/0/0
R /24 [120/2] via , 00:00:12,Serial0/0/0
R /28 [120/2] via , 00:00:12,Serial0/0/0
R /16 [120/2] via , 00:00:03, Serial0/0/0
/24 is variably subnetted, 5 subnets, 2 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R /30 [120/1]via ,0:0:12,Serial0/0/0
C /30 is directly connected, Serial0/0/1
L /30 is directly connected, Serial0/0/1
R1#
Packet with Destination IPv4 address
No Level 1 Ultimate Routes match
Matches Level 1 Parent Route (minimum match is classful mask).
Look for matching Child route
At a minimum it must match the number of bits in the route as indicated by the subnet mask.
If more than one child route matches choose routes with longest match.

48. Packet with Destination IPv4 address 172.16.5.10
R1#show ip route | begin Gateway
Gateway of last resort is to network
S* /0 [1/0] via , Serial0/0/1
is directly connected, Serial0/0/1
/16 is variably subnetted, 5 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
R /24 [120/1] via , 00:00:12,Serial0/0/0
R /24 [120/2] via , 00:00:12,Serial0/0/0
R /28 [120/2] via , 00:00:12,Serial0/0/0
R /16 [120/2] via , 00:00:03, Serial0/0/0
/24 is variably subnetted, 5 subnets, 2 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R /30 [120/1]via ,0:0:12,Serial0/0/0
C /30 is directly connected, Serial0/0/1
L /30 is directly connected, Serial0/0/1
R1#
Packet with Destination IPv4 address

49. L 209.165.200.233/30 is directly connected, Serial0/0/1 R1# 10.1.2.3
R1#show ip route | begin Gateway
Gateway of last resort is to network
S* /0 [1/0] via , Serial0/0/1
is directly connected, Serial0/0/1
/16 is variably subnetted, 5 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
R /24 [120/1] via , 00:00:12,Serial0/0/0
R /24 [120/2] via , 00:00:12,Serial0/0/0
R /28 [120/2] via , 00:00:12,Serial0/0/0
R /16 [120/2] via , 00:00:03, Serial0/0/0
/24 is variably subnetted, 5 subnets, 2 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R /30 [120/1]via ,0:0:12,Serial0/0/0
C /30 is directly connected, Serial0/0/1
L /30 is directly connected, Serial0/0/1
R1#
Packet with Destination IPv4 address
No Level 1 Ultimate Routes to choose match
No Level 1 Parent Routes match
Look for Level 1 supernet route (mask less than classful mask), including default
Choose longest match.
Default route always matches because 0 bits have to match.
0 matching bits makes it the “gateway of last resort”

50. 10.1.2.3 R1# R1#show ip route | begin Gateway
/16 is variably subnetted, 5 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
R /24 [120/1] via , 00:00:12,Serial0/0/0
R /24 [120/2] via , 00:00:12,Serial0/0/0
R /28 [120/2] via , 00:00:12,Serial0/0/0
R /16 [120/2] via , 00:00:03, Serial0/0/0
/24 is variably subnetted, 5 subnets, 2 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R /30 [120/1]via ,0:0:12,Serial0/0/0
C /30 is directly connected, Serial0/0/1
L /30 is directly connected, Serial0/0/1
R1#
Packet with Destination IPv4 address
No default route
No Level 1 Ultimate Routes to choose match
No Level 1 Parent Routes match
No supernet routes match
Drop packet

51. IPv6 Routing Tables

52. There is no level 1 parent of level 2 child routes.
R1# show ipv6 route
<Output omitted>
C :DB8:CAFE:1::/64 [0/0]
via GigabitEthernet0/0, directly connected
L :DB8:CAFE:1::1/128 [0/0]
via GigabitEthernet0/0, receive
D :DB8:CAFE:2::/64 [90/ ]
via FE80::3, Serial0/0/1
D :DB8:CAFE:3::/64 [90/ ]
C :DB8:CAFE:A001::/64 [0/0]
via Serial0/0/0, directly connected
L :DB8:CAFE:A001::1/128 [0/0]
via Serial0/0/0, receive
D :DB8:CAFE:A002::/64 [90/ ]
C :DB8:CAFE:A003::/64 [0/0]
via Serial0/0/1, directly connected
L :DB8:CAFE:A003::1/128 [0/0]
via Serial0/0/1, receive
L FF00::/8 [0/0]
via Null0, receive
R1#
Components of the IPv6 routing table are very similar to the IPv4 routing table (directly connected interfaces, static routes, and dynamically learned routes).
There is no concept of classes in IPv6, so all routes are effectively level 1 ultimate routes.
There is no level 1 parent of level 2 child routes.
IPv6 Routing Table Entries

53. Reference IPv6 Topology
EIGRP for IPv6 Routing Domain
2001:DB8:CAFE:2::/64
LLA: FE80::2
G0/0 :1
S0/0/0 :2 R2
S0/0/1 :1
2001:DB8:CAFE:A001::/64
2001:DB8:CAFE:A002::/64
64 kbps
S0/0/0 :1
1024 kbps
S0/0/1 :2
LLA: FE80::1
1544 kbps
LLA: FE80::3
S0/0/1 :1
S0/0/0 :2 R1 R3
2001:DB8:CAFE:A003::/64
G0/0 :1
G0/0 :1
2001:DB8:CAFE:1::/64
2001:DB8:CAFE:3::/64
Media Description:
Use graphic from powerpoint

54. Directly Connected Networks of R1
R1# show ipv6 route
C :DB8:CAFE:1::/64 [0/0]
via GigabitEthernet0/0, directly connected
L :DB8:CAFE:1::1/128 [0/0]
via GigabitEthernet0/0, receive
D :DB8:CAFE:2::/64 [90/ ]
via FE80::3, Serial0/0/1
D :DB8:CAFE:3::/64 [90/ ]
C :DB8:CAFE:A001::/64 [0/0]
via Serial0/0/0, directly connected
L :DB8:CAFE:A001::1/128 [0/0]
via Serial0/0/0, receive
D :DB8:CAFE:A002::/64 [90/ ]
C :DB8:CAFE:A003::/64 [0/0]
via Serial0/0/1, directly connected
L :DB8:CAFE:A003::1/128 [0/0]
via Serial0/0/1, receive
L FF00::/8 [0/0]
via Null0, receive
R1#
Media Description:
Create as indicated

55. Remote Network Entries on R1
R1# show ipv6 route
C :DB8:CAFE:1::/64 [0/0]
via GigabitEthernet0/0, directly connected
L :DB8:CAFE:1::1/128 [0/0]
via GigabitEthernet0/0, receive
D :DB8:CAFE:2::/64 [90/ ]
via FE80::3, Serial0/0/1
D :DB8:CAFE:3::/64 [90/ ]
C :DB8:CAFE:A001::/64 [0/0]
via Serial0/0/0, directly connected
L :DB8:CAFE:A001::1/128 [0/0]
via Serial0/0/0, receive
D :DB8:CAFE:A002::/64 [90/ ]
C :DB8:CAFE:A003::/64 [0/0]
via Serial0/0/1, directly connected
L :DB8:CAFE:A003::1/128 [0/0]
via Serial0/0/1, receive
L FF00::/8 [0/0]
via Null0, receive
R1#
Media Description:
Create as indicated

56. Chapter 3 Routing Dynamically
CIS 82 Routing Protocols and Concepts
Rick Graziani
Cabrillo College
Version 6