Cisco Networking Academy Program Semester 5 : Routing

1
Cisco Networking Academy Program Semester 5
Routing

• Chapter 2
• IP Addressing

2
IP Addressing

• IPv4 Addressing
• IP Addressing Crisis and Solutions
• VLSM
• Route Summarization
• Private Addressing and NAT
• IP Unnumbered
• DHCP and Easy IP
• Helper Addresses
• IPv6

3
IPv4 Adressing

• 32 bits addresses
• Divided into 4 bytes
• A network and a host field determined by a subnet
  mask
• Written in dotted decimals

4
Address Classes

• Class D Multicast 224-239 (to a group of users)
• Class E Reserved for experimental purposes 240
  and up
• Broadcast 255.255.255.255
• Loopback 127.0.0.1

5
Subnet Masking

• Borrows bits to the host field of the address to
  create sub-networks
• Gives more flexibility
• Allows better control of broadcasts
• Network address calculated with subnet mask (AND)

6
Solution to Address Crisis

• IPv6 (128 bit addresses)
• Better use of existing IPv4
• VLSM
• Route Summarization
• Private Addressing and NAT
• IP Unnumbered

7
Limits To Classful Addressing

• Classful protocols dont carry subnet masks.
• Classful protocols (RIP ver.1, IGRP) arent
  flexible.
• Oversized routing tables
• Important waste of addresses

8
Limits To Classful Addressing

• (config) IP classless (default on ver.12.0)
  allows routing of packets between remote subnets
  of the same network)

(config) ip route 172.2.3.0 255.255.255.0
172.2.2.1
172. 2. 2. 0
(config) IP classless
172. 2. 2. 0
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Classless Inter-Domain Routing (CIDR)

• Internet addresses are managed by the three
  Regional Internet Registries (ARIN, RIPE NCC,
  APNIC)
• RIRs allocate address ranges (CIDR blocks)
  regardless of classful boundaries
• Uses summarization
• Reduces routing tables size, CPU cycles and
  memory requirement.

10
Summarization
11
Summarization, Aggregation And Super-netting

• 3 terms, one meaning
• Super-netting is usually used for
• aggregation of contiguous Classful network
• Under the same administration

12
Class C Super-netting Example

• The company XYZ needs 400 addresses.
• Instead of using a whole class B, it uses only 2
  contiguous class C networks.

13
Variable Length Subnet Masks (VLSM)
14
Classful And Classless Protocols

• RIP version 1
• does not send subnet mask information in its
  updates. (no VLSM nor CIDR)
• updates are broadcast increasing network traffic.
  
• does not support authentication.

• RIP Version 2
• sends subnet information (VLSM and CIDR),
• multicast routing updates (224.0.0.9), providing
  better efficiency,
• provides for authentication in its updates.

15
Summarization and Route Flapping
Summarization prevents the propagation of
multiple routing updates triggered by route
flapping
16
Private IP addresses

• Defined by RFC 1918
• Not routed on the Internet
• Used for LAN routing and on private Backbones
• Relies on NAT to reach public networks

17
Dealing with Discontiguous Subnets

• Issue with RIP Version 2 and EIGRP
• (config) no auto-summary

18
Network Address Translation (NAT)

• Defined by RFC 1631
• Translates private addresses into globally
  significant ones.
• NAT Overloading or Port Address Translation (PAT)
  translates many privates addresses into a single
  public one, using port numbers.

19
IP Unnumbered

• An interface borrows the IP Address of an other
  interface.

20
DHCP

• Dynamic Host Configuration Protocol
• Provides IP configuration parameters to hosts
• More powerful than BootP
• Limited server available on Cisco IOS

21
Configuring DHCP
22
Cisco Easy IP

• Dynamically configures a WAN Interface over a
  point-to-point connection
• Provides LAN addresses to local network
• Provides NAT

23
Helper Address

• Changes a broadcast frame into the unicast
  forwarded to the server address

24
Configuring IP Helper
Default forwarding
25
IP V.6

• 128 bits address format
• Expressed in hexadecimal
• Fields represent the different parts of a 4 level
  hierarchy