1. Unit 7 Advanced IP Routing Chapter 19 to 21
© 2011 ITT Educational Services Inc.
NT-2640 Advanced Networking: Unit 7: Slide 1

2. Class Agenda 14/25/16
Learning Objectives
Unit 7: Discussions and Video
Lab Activities will be done in class.
Assignments will be given in class.
Break Times. 10 Minutes break in every 1 Hour.
Note: Submit all Assignment and labs due today.

3. VLSM
VLSM occurs when an internetwork uses more than one mask in different subnets of a single Class A, B, or C network.
VLSM allows engineers to reduce the number of wasted IP addresses in each subnet
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 3

4. Classless and Classful Routing Protocols
For a routing protocol to support VLSM, the routing protocol must advertise not only the subnet number but also the subnet mask when advertising routes.
A routing protocol must include subnet masks in its routing updates to support manual route summarization.
Ensure that there is no overlapping VLSM Subnet
Shorter prefix lengths (meaning more host bits) for larger numbers of hosts/subnet, and longer prefix lengths (meaning fewer host bits) for smaller numbers of hosts/subnet.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 4

5. Subnets and Address Ranges in Figure 5-2
Subnet Location
Subnet Number
First Address
Last Address
Broadcast Address
R1 LAN
R2 LAN
R3 LAN
R1-R2 serial
R1-R3 serial
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 5

6. Generic Subnets Chart Table 18-1 Generic List-All-Subnets Chart Octet2 3 4
Mask
Magic Number
Network Number/Zero Subnet
Next Subnet
Last Subnet
Broadcast Subnet
Out of Range (Used by Process)
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 6: Slide 6

7. Classless and Classful Routing Protocols
For a routing protocol to support VLSM, the routing protocol must advertise not only the subnet number but also the subnet mask when advertising routes.
A routing protocol must include subnet masks in its routing updates to support manual route summarization.
Each IP routing protocol is considered to be either classless or classful , based on whether the routing protocol does (classless) or does not (classful) send the mask in routing updates.
Each routing protocol is either classless or classful by its very nature; no commands exist to enable or disable whether a particular routing protocol is a classless or classful routing protocol.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 7

8. Manual Route Summarization
Small networks might have only a few dozen routes in their routers’ routing tables.
The larger the network, the larger the number of routes.
The routing table might become too large in large IP networks. As routing tables grow, they consume more memory in a router.
And with a large routing table, it takes more time to troubleshoot problems, because the engineers working on the network need to sift through more information.
Route summarization reduces the size of routing tables while maintaining routes to all the destinations in the network.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 8

9. Route Summarization Concepts
Engineers use route summarization to reduce the size of the routing tables in the network.
Route summarization works much better when the network was designed with route summarization in mind.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 9

10. Autosummarization And Manual summarization
Manual route summarization can improve routing efficiency, reduce memory consumption, and improve convergence by reducing the length of routing tables.
Automatic summarization of routes at the boundaries of classful networks, uses a feature called autosummarization.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 10

11. Autosummarization Support and Configuration
Classful routing protocols must use autosummarization. Some classless routing protocols support autosummarization, defaulting to use it, but with the ability to disable it with the no auto-summary router subcommand.
Below summarizes the facts about autosummarization on Cisco routers.
Autosummarization Support and Defaults
Routing Protocol
Classless?
Supports Autosummarization?
Defaults to Use Autosummarization?1
Can Disable Autosummarization?
RIP-1 No
Yes
RIP-2
EIGRP
OSPF —
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 11

12. Chapter 20 “Troubleshooting II”
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 12

13. The ping and traceroute Commands
Internet Control Message Protocol (ICMP)
TCP/IP includes ICMP, a protocol designed to help manage and control the operation of a TCP/IP network.
The ICMP protocol provides a wide variety of information about a network’s health and operational status.
ICMP is considered part of TCP/IP’s network layer. It helps control IP, it can provide useful troubleshooting information.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 13

14. PING Command The ping Command and the ICMP Echo Request and Echo Reply
The ping command uses the ICMP Echo Request and Echo Reply messages.
The Echo Request simply means that the host to which it is addressed should reply to the packet.
The Echo Reply is the ICMP message type that should be used in the reply.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 14

15. The Ping Command
The ping command lists various responses that in some cases imply that an unreachable message was received.
ping Command Code
Description !
ICMP Echo Reply received .
Nothing was received before the ping command timed out U
ICMP unreachable (destination) received N
ICMP unreachable (network/subnet) received M
ICMP Can’t Fragment message received ?
Unknown packet received
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 15

16. The traceroute Command
The ping command is a powerful troubleshooting tool that can be used to answer the question “Does the route from here to there work?”
The traceroute command provides an arguably better troubleshooting tool because not only can it determine if the route works, but it can supply the IP address of each router in the route.
If the route is not working, traceroute can identify the best places to start troubleshooting the problem.
The IOS traceroute command uses the Time Exceeded message and the IP TTL field to identify each successive router in a route.
The traceroute command sends a set of messages with increasing TTL values, starting with 1.
The traceroute command expects these messages to be discarded when routers decrement the TTL to 0, returning Time Exceeded messages to the traceroute command. The source IP addresses of the Time Exceeded messages identify the routers that discarded the messages, which can then be displayed by the traceroute command.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 7: Slide 16

17. All answers to overdue labs should be submitted in the next class.
Lab Activities.
Complete 7 Lab in class.
All answers to overdue labs should be submitted in the next class.
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 4: Slide 17

18. Unit 7 assignment will be given in class.
Reading Assignment: Read chapter 22 and 23
© 2011 ITT Educational Services Inc.
NT-2640 Wan Technologies: Unit 4: Slide 18