1 © 2003, Cisco Systems, Inc. All rights reserved. CCNP 1 v3.0 Module 2 Advanced IP Addressing Management Cisco Networking Academy

222 © 2003, Cisco Systems, Inc. All rights reserved. Objectives IPv4 Addressing IP Addressing Crisis and Solutions VLSM Route Summarization Private Addressing and NAT IP Unnumbered DHCP and Easy IP Helper Addresses IPv6

333 © 2003, Cisco Systems, Inc. All rights reserved. Address Architecture of the Internet Dotted Decimal Notation

444 © 2003, Cisco Systems, Inc. All rights reserved. Class A and B IP addresses

555 © 2003, Cisco Systems, Inc. All rights reserved. IPv4 Address Classes Class A Class B Class C NetworkHost Network Host Network Host 1st octet2nd octet3rd octet4th octet

666 © 2003, Cisco Systems, Inc. All rights reserved. IP Addresses Available to Internet Hosts

777 © 2003, Cisco Systems, Inc. All rights reserved. One Problem - No Medium Size 16 million 65, For most organizations, 256 is too small a limit on hosts, yet 65,536 is far too many.

888 © 2003, Cisco Systems, Inc. All rights reserved. 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

999 © 2003, Cisco Systems, Inc. All rights reserved. Subnet Masking

10 © 2003, Cisco Systems, Inc. All rights reserved. IP Addressing Crisis

11 © 2003, Cisco Systems, Inc. All rights reserved. Classless Interdomain Routing (CIDR)

12 © 2003, Cisco Systems, Inc. All rights reserved. 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

13 © 2003, Cisco Systems, Inc. All rights reserved. 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

14 © 2003, Cisco Systems, Inc. All rights reserved. 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.

15 © 2003, Cisco Systems, Inc. All rights reserved. Classless and Classful Routing Protocols

16 © 2003, Cisco Systems, Inc. All rights reserved. Supernetting and Address Allocation

17 © 2003, Cisco Systems, Inc. All rights reserved. Route Aggregation and Supernetting 1 st octet2 nd octet

18 © 2003, Cisco Systems, Inc. All rights reserved. Route Summarization

19 © 2003, Cisco Systems, Inc. All rights reserved. Private IP Addresses (RFC 1918)

20 © 2003, Cisco Systems, Inc. All rights reserved. Discontiguous Subnets

21 © 2003, Cisco Systems, Inc. All rights reserved. Network Address Translation (NAT)

22 © 2003, Cisco Systems, Inc. All rights reserved. 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 / /24

23 © 2003, Cisco Systems, Inc. All rights reserved. DHCP Overview: Step 1

24 © 2003, Cisco Systems, Inc. All rights reserved. DHCP Overview: Step 2

25 © 2003, Cisco Systems, Inc. All rights reserved. DHCP Operation

26 © 2003, Cisco Systems, Inc. All rights reserved. Key DHCP Server Commands

27 © 2003, Cisco Systems, Inc. All rights reserved. Key Commands for Monitoring DHCP Operation

28 © 2003, Cisco Systems, Inc. All rights reserved. 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.

29 © 2003, Cisco Systems, Inc. All rights reserved. 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

30 © 2003, Cisco Systems, Inc. All rights reserved. Purpose of Helper Addresses

31 © 2003, Cisco Systems, Inc. All rights reserved. Default Forwarded UDP Services Router(config-if)#exi Router(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 571 Router(config)#no ip forward-protocol udp 69 To add a forwarded protocol

32 © 2003, Cisco Systems, Inc. All rights reserved. IP Helper Address Example Router(config)#int fa0/1 Router(config-if)#ip helper-address

33 © 2003, Cisco Systems, Inc. All rights reserved. IP Address Issues Solutions Growth of Routing Tables

34 © 2003, Cisco Systems, Inc. All rights reserved. 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.

35 © 2003, Cisco Systems, Inc. All rights reserved. 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

36 © 2003, Cisco Systems, Inc. All rights reserved. IPv6 IPv6 will most likely coexist with IPv4 for years to come. Some experts believe IPv4 will remain for more than 10 more years.

37 © 2003, Cisco Systems, Inc. All rights reserved. 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:

38 © 2003, Cisco Systems, Inc. All rights reserved. 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

39 © 2003, Cisco Systems, Inc. All rights reserved. IPv6 Loopback address 0:0:0:0:0:0:0:1 (the IPv6 loopback address) Can be written list this: : :1

40 © 2003, Cisco Systems, Inc. All rights reserved. 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

41 © 2003, Cisco Systems, Inc. All rights reserved. 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.

42 © 2003, Cisco Systems, Inc. All rights reserved. IPv6 address format IPv6 address has three levels of hierarchy

43 © 2003, Cisco Systems, Inc. All rights reserved. Summary