1 © 2003, cisco systems, inc. all rights reserved. ccnp 1 v3.0 module 2 advanced ip addressing...

1© 2003, Cisco Systems, Inc. All rights reserved.

CCNP 1 v3.0 Module 2 Advanced IP Addressing

ManagementCisco Networking Academy


Objectives

• IPv4 Addressing

• IP Addressing Crisis and Solutions

• VLSM

• Route Summarization

• Private Addressing and NAT

• IP Unnumbered

• DHCP and Easy IP

• Helper Addresses

• IPv6


Address Architecture of the Internet

Dotted Decimal Notation


Class A and B IP addresses


IPv4 Address Classes

Class A

Class B

Class C

Network Host Host Host

Network Network Host Host

Network Network Network Host

1st octet 2nd octet 3rd octet 4th octet


IP Addresses Available to Internet Hosts


One Problem - No Medium Size

• 16 million

• 65,536

• 256

For most organizations, 256 is too small a limit on hosts, yet 65,536 is far too many.


The Subnet Mask

• The solution to the IP address shortage was thought to be the subnet mask.

• Formalized in 1985 (RFC 950), the subnet mask breaks a single class A, B or C network in to smaller pieces.

Subnetting


Subnet Masking


IP Addressing Crisis


Classless Interdomain Routing (CIDR)


Variable-Length Subnet Masks (VLSM)

• VLSM allows an organization to use more than one subnet mask within the same network address space.

• Implementing VLSM is often referred to as subnetting a subnet and it can be used to maximize addressing efficiency.

• Over the past 20 years, network engineers have developed three critical strategies for efficiently addressing point-to-point WAN links:

Use VLSM

Use private addressing (RFC 1918)

Use IP unnumbered


Enabling the use of subnet 0

• The Cisco IOS allows you to use subnet 0. On pre-IOS 12.x releases, this feature is not enabled by default:

router(config)#ip subnet-zero


Using the all-ones subnet

• Although this Cisco IOS will allow you to configure addresses in the all-ones subnet.

• Some literature still states that, as a general rule, you should not use the all-ones subnet.

However, it is perfectly legal to use these addresses according to the RFCs.


Classless and Classful Routing Protocols


Supernetting and Address Allocation


Route Aggregation and Supernetting

1st octet 2nd octet


Route Summarization


Private IP Addresses (RFC 1918)


Discontiguous Subnets


Network Address Translation (NAT)


Using IP Unnumbered

This is fine as long as both of the routers have a route for the address used for in the unnumbered configuration.

•Default routes will work too

These ‘unnumbered’ addresses do not need to be on the same subnet

168.71.8.0/24 168.71.5.0/24


DHCP Overview: Step 1


DHCP Overview: Step 2


DHCP Operation


Key DHCP Server Commands


Key Commands for Monitoring DHCP Operation


Easy IP

• Easy IP is a combination suite of Cisco IOS features that allows a router to negotiate its own IP address and to do

NAT through that negotiated address.


Easy IP

• Easy IP is a combination suite of Cisco IOS features that allows a router to negotiate its own IP address and to do NAT through that negotiated address.

• Easy IP is typically deployed on a small office, home office (SOHO) router.

• It is useful in cases where a small LAN connects to the Internet by way of a provider that dynamically assigns only one IP address for the entire remote site.

– DHCP or PPPoE

http://www.cisco.com/warp/public/cc/pd/iosw/ioft/ionetn/tech/ezip1_wp.htm


Purpose of Helper Addresses


Default Forwarded UDP Services

Router(config-if)#exiRouter(config)#ip forward-protocol ? nd Sun's Network Disk protocol sdns Network Security Protocol spanning-tree Use transparent bridging to flood UDP broadcasts turbo-flood Fast flooding of UDP broadcasts udp Packets to a specific UDP port

Router(config)#ip forward-protocol udp 571Router(config)#no ip forward-protocol udp 69

To add a forwarded protocol


IP Helper Address Example

Router(config)#int fa0/1Router(config-if)#ip helper-address 172.24.1.9


IP Address Issues Solutions

Growth of Routing Tables


Long-term solution: IPv6

• IP v6, or IPng (IP – the Next Generation) uses a 128-bit address space, yielding

340,282,366,920,938,463,463,374,607,431,768,211,456

possible addresses.


IPv6

• IPv6 has been slow to arrive

– IPv4 revitalized by new features, making IPv6 a luxury, and not a desperately needed fix

• (RFC 1918 address, VLSM)

– IPv6 requires new software; IT staffs must be retrained


IPv6

• IPv6 will most likely coexist with IPv4 for years to come.

Some experts believe IPv4 will remain for more than 10 more years.


IPv6 address format

• IPv6 can be written as 32 hex digits, with colons separating the values of the eight 16-bit pieces of the address:

FEDC:BA98:7654:3210:FEDC:BA98:7654:3210

http://www.faqs.org/rfcs/rfc1884.htmlhttp://www.faqs.org/rfcs/rfc2373.html


IPv6 address format

Because IPv6 addresses, especially in the early implementation phase, may contain consecutive 16-bit values of zero, one such string of 0s per address can be omitted and replaced by a double colon, so this:

1080:0:0:0:8:800:200C:417A

can be shortened to become this:

1080::8:800:200C:417A


IPv6 Loopback address

0:0:0:0:0:0:0:1

(the IPv6 loopback address)

Can be written list this:

: :1

http://playground.sun.com/pub/ipng/html/INET-IPng-Paper.html


IPv6 Address Format

• Three general types of addresses:

Unicast

Anycast

Mulicast

• IPv6 global unicast addresses feature three levels of hierarchy:

Public topology

Site topology

Interface Identifier


IPv6 Address format

• Unicast: An identifier for a single interface.

• Anycast: An identifier for a set of interfaces (typically belonging to different nodes). A packet sent to an anycast address is delivered to the “nearest,” or first, interface in the anycast group.

• Multicast: An identifier for a set of interfaces (typically belonging to different nodes). A packet sent to a multicast address is delivered to all interfaces in the multicast group.


IPv6 address format

IPv6 address has three levels of hierarchy


Summary

1 © 2003, cisco systems, inc. all rights reserved. ccnp 1 v3.0 module 2 advanced ip addressing...

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