Supernetting questions and answers pdf

NW/Questions.docx
PC & Industrial Networks

70 Points

Answer each of the following questions in complete detail:

1. (10 points) Assume a host computer has the following configuration:

IP Address: 200.110.84.176

Subnet Mask: 255.255.248.0

Default Gateway: 200.110.84.1

a. What is the Class of this ‘network’?

b. Is this a Network, Subnetwork, Supernetwork or something else? How do you know?

c. How many possible hosts would there be on the above network if all usable addresses were assigned?

d. How would this IP address be expressed using CIDR notation?

e. Using CIDR notation, what is the range of the block of addresses this Host belongs to?

2. (6 points) Explain everything that can be determined from the following:

a. fe80::9890:96ff:fea1:53ed%12

b. 2002:77fe:8921::77fe:8921

c. ::01

d. ::

3. (4 points) What is the significance of the ninth octet in the header of the IP datagram?

4. (5 points) SSK Corp has offices in Toledo, Detroit and Columbus. Each office has 127

Computers. The IT plan calls for connecting all offices using data lines. The Toledo site will also connect to the Internet. SSK Corp. has elected to use PUBLIC IP address space on all computers at each of its sites.

Their ISP has restricted the IP ranges to the ones below. The ISP’s Network

Administrator is on vacation – you have been asked to fill-in and select a range of addresses that will satisfy SSK Corp.’s needs with the least amount of wasted IP addresses. Propose a range of addresses for SSK Corp. and explain your answer.

225.113.8.0/24

225.113.9.0/24

192.168.0.0/16

221.127.136.0/24

221.128.135.0/24

221.128.136.0/24

221.128.137.0/24

221.128.138.0/24

206.122.148.0/24

10.0.0.0/8

221.125.138.0/24

221.126.137.0/25

221.128.139.0/24

5. (5 points) Using the IP ranges below:

a) What IP range would an ISP provide to a customer, if the customer wanted a range of Public IP’s for use on the Internet? Explain your choice and why you feel the other choices are not adequate?

b) Using the Range you selected in ‘5a’ above - subnet the range into as many /28 networks as possible – show your work and each /28 range of addresses. (Show the network address and the broadcast address for each /28 subnet)

225.113.8.0/24

225.113.9.0/25

192.168.0.0/16

201.127.136.0/24

172.16.0.0/24

10.0.0.0/8

169.254.137.0/25

245.125.1378.0/24

10.0.0.0/24

245.0.0.0/8

127.0.0.0/8

6. (15 points) The following information was extracted from an Ethernet Frame:

IP Datagram Header: 45 00 00 44 5b d2 00 00 80 11 ef 4d 83 b7 75 39 83 b7 72 e1

Based on the above information, describe everything that can be determined about this packet (give the actual data value for each field). Convert each field to its normally displayed value (i.e. Hexadecimal/Decimal/Binary).

Example: Version is 4 which is IPv4

7. (10 points) Bob obtained the following information from a workstation: C:\>ipconfig

Ethernet adapter Local Area Connection:

IP Address. . . . . . . ……... . : 169.254.10.105 Subnet Mask . . . . . . ……... : 255.255.0.0 Default Gateway . . . . ……..:

Link-Local IPv6 Address…..fe80::9890:96ff:fea1:53ed%12

a. Explain everything that can be determined about this host.

After waiting 5 minutes and making no changes to his workstation. Bob obtained the following information from his workstation.

C:\>ipconfig

Ethernet adapter Local Area Connection:

IP Address. . . . . . . . ………………: 138.110.10.50 Subnet Mask . . . . . . …………….. : 255.255.0.0

Default Gateway . . . …………….. : 138.110.10.1

Link-Local IPv6 Address………….:fe80::9890:96ff:fea1:53ed%12

b. How would you explain the changes to the IP stack? Explain in detail what occurred.

8. (5 points) Explain each of the good ‘Network Design goals’ as discussed in class.

9. (10 points) You have been given the task of changing the IP Address and enabling telnet remote access on a CISCO 2950 enterprise switch.

The current IP address is 172.25.2/16 the new IP address is 10.0.0.2/24

The enterprise switch has no password configured.

a. Explain all of the commands needed for you to successfully accomplish the IP Address change and telnet remote access.

NW/Useful files/bootstapping.pdf
Before a device on a TCP/IP network can effectively communicate, it needs to know its IP address. While a conventional network host can read this information from its internal disk, some devices have no storage, and so do not have this luxury. They need help from another device on the network to provide them with an IP address and other information and/or software they need to become active IP hosts. This problem of getting a new machine up and running is commonly called bootstrapping, and to provide this capability to IP hosts, the TCP/IP Bootstrap Protocol (BOOTP) was created.

Without a form of internal storage, a device must rely on someone or something to tell it “who it is” (its address) and how to function each time it is powered up. When a device like this is turned on, it is in a difficult position: it needs to use IP to communicate with another device that will tell it how to communicate using IP! This process, called bootstrapping or booting, comes from an analogy to a person “pulling himself up using his own bootstraps”.

The Reverse Address Resolution Protocol (RARP) was the first attempt to resolve this “bootstrap problem”. Created in 1984, RARP is a direct adaptation of the low-level Address Resolution Protocol (ARP) that binds IP addresses to link-layer hardware addresses. RARP is capable of providing a diskless device with its IP address, using a simple client/server exchange of a request and reply between a host and an RARP server.

The difficulty with RARP is that it has so many limitations. It operates at a fairly low level using hardware broadcasts, so it requires adjustments for different hardware types. An RARP server is also required on every physical network to respond to layer-two broadcasts. Each RARP server must have address assignments manually provided by an administrator. And perhaps worst of all, RARP only provides an IP address to a host and none of the other information a host may need.

RARP clearly wasn't sufficient for the host configuration needs of TCP/IP. To support both the needs of diskless hosts and other situations where the benefits of autoconfiguration were required, the Bootstrap Protocol (BOOTP) was created. BOOTP was standardized in RFC 951, published September 1985. This relatively straight- forward protocol was designed specifically to address the shortcomings of RARP:

BOOTP Deals With the First Phase of Bootstrapping

It should be noted that even though the name of BOOTP implies that it defines everything needed for a storageless device to “boot”, this isn't really the case. As the BOOTP standard itself describes, “bootstrapping” generally requires two phases. In the first, the client is provided with an address and other parameters. In the second, the client downloads software, such as an operating system and drivers, that let it function on the network and perform whatever tasks it is charged with. BOOTP really only deals with the first of these phases: address assignment and configuration. The second is assumed to take place using a simple file transfer protocol like the Trivial File Transfer Protocol (TFTP).

http://www.tcpipguide.com/free/t_TCPIPBootstrapProtocolBOOTP.htm
http://www.tcpipguide.com/free/t_ReverseAddressResolutionandtheTCPIPReverseAddressR.htm
http://www.tcpipguide.com/free/t_TCPIPAddressResolutionProtocolARP.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-2.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-2.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-2.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-2.htm
http://www.tcpipguide.com/free/t_TrivialFileTransferProtocolTFTP.htm
http://www.tcpipguide.com/free/t_TrivialFileTransferProtocolTFTP.htm
Changes to BOOTP and the Development of DHCP

BOOTP was the TCP/IP host configuration of choice from the mid-1980s through the end of the 1990s. The vendor extensions introduced in RFC 1048 were popular, and over the years, additional vendor extensions were defined; RFC 1048 was replaced by RFCs 1084, 1395 and 1497 in succession. Some confusion also resulted over the years in how some sections of RFC 951 should be interpreted, and how certain features of BOOTP work.

RFC 1542, Clarifications and Extensions for the Bootstrap Protocol, was published in October 1993 to address this, and also made some slight changes to the protocol's operation. (RFC 1542 is actually a correction of the nearly-identical RFC 1532 that had some small errors in it.)

While BOOTP was obviously quite successful, it also had certain weaknesses of its own. One of the most important of these is lack of support for dynamic address assignment. The need for dynamic assignment became much more pronounced when the Internet really started to take off in the late 90s. This led directly to the development of the Dynamic Host Configuration Protocol (DHCP).

While DHCP replaced BOOTP as the TCP/IP host configuration protocol of choice, it would be inaccurate to say that BOOTP is “gone”. It is still used to this day in various networks. Furthermore, DHCP was based directly on BOOTP, and they share many attributes, including a common message format. BOOTP vendor extensions were used as the basis for DHCP options, which work in the same way but include extra capabilities. In fact, the successor to RFC 1497 is RFC 1533, which officially merges BOOTP vendor extensions and BOOTP options into the same standard.

http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-3.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-3.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-3.htm
http://www.tcpipguide.com/free/t_TCPIPDynamicHostConfigurationProtocolDHCP.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-3.htm
http://www.tcpipguide.com/free/t_BOOTPOverviewHistoryandStandards-3.htm
NW/Useful files/DHCP_APIPA(1).pdf
NW/Useful files/IPClasses.pdf
Classes

The following are the classes of IP addresses.

 Class A—The first octet denotes the network address, and the last three octets are the host portion. Any IP address whose first octet is between 1 and 126 is a Class A address. Note that 0 is reserved as a part of the default address, and 127 is reserved for internal loopback testing.

1-126

 Class B—The first two octets denote the network address, and the last two octets are the host portion. Any address whose first octet is in the range 128 to 191 is a Class B address.

128-191

 Class C—The first three octets denote the network address, and the last octet is the host portion. The first octet range of 192 to 223 is a Class C address.

192-223

 Class D—Used for multicast. Multicast IP addresses have their first octets in the range 224 to 239.

224-239 (Multicast)

 Class E—Reserved for future use and includes the range of addresses with a first octet from 240 to 255.

240-255 (Reserved)

Subnetting

Subnetting is the concept of dividing the network into smaller portions called subnets. This is done by borrowing bits from the host portion of the IP address, enabling more efficient use of the network address. A subnet mask

defines which portion of the address is used to identify the network and which denotes the hosts.

The following tables show all possible ways a major network can be subnetted, and, in each case, how many effective subnets and hosts are possible.

There are three tables, one for each class of addresses.

 The first column shows how many bits are borrowed from the host portion of the address for subnetting.

 The second column shows the resulting subnet mask in dotted decimal format.

 The third column shows how many subnets are possible.

 The fourth column shows how many valid hosts are possible on each of these subnets.

 The fifth column shows the number of subnet mask bits.

Class A Host/Subnet Table

Class A

Number of

Bits Borrowed Subnet Effective Number of Number of Subnet

from Host Portion Mask Subnets Hosts/Subnet Mask Bits

------- --------------- --------- ------------- -------------

1 255.128.0.0 2 8388606 /9

2 255.192.0.0 4 4194302 /10

3 255.224.0.0 8 2097150 /11

4 255.240.0.0 16 1048574 /12

5 255.248.0.0 32 524286 /13

6 255.252.0.0 64 262142 /14

7 255.254.0.0 128 131070 /15

8 255.255.0.0 256 65534 /16

9 255.255.128.0 512 32766 /17

10 255.255.192.0 1024 16382 /18

11 255.255.224.0 2048 8190 /19

12 255.255.240.0 4096 4094 /20

13 255.255.248.0 8192 2046 /21

14 255.255.252.0 16384 1022 /22

15 255.255.254.0 32768 510 /23

16 255.255.255.0 65536 254 /24

17 255.255.255.128 131072 126 /25

18 255.255.255.192 262144 62 /26

19 255.255.255.224 524288 30 /27

20 255.255.255.240 1048576 14 /28

21 255.255.255.248 2097152 6 /29

22 255.255.255.252 4194304 2 /30

23 255.255.255.254 8388608 2* /31

Class B Host/Subnet Table

Class B Subnet Effective Effective Number of Subnet

Bits Mask Subnets Hosts Mask Bits

------- --------------- --------- --------- -------------

1 255.255.128.0 2 32766 /17

2 255.255.192.0 4 16382 /18

3 255.255.224.0 8 8190 /19

4 255.255.240.0 16 4094 /20

5 255.255.248.0 32 2046 /21

6 255.255.252.0 64 1022 /22

7 255.255.254.0 128 510 /23

8 255.255.255.0 256 254 /24

9 255.255.255.128 512 126 /25

10 255.255.255.192 1024 62 /26

11 255.255.255.224 2048 30 /27

12 255.255.255.240 4096 14 /28

13 255.255.255.248 8192 6 /29

14 255.255.255.252 16384 2 /30

Class C Host/Subnet Table

Class C Subnet Effective Effective Number of Subnet

Bits Mask Subnets Hosts Mask Bits

------- --------------- --------- --------- --------------

1 255.255.255.128 2 126 /25

2 255.255.255.192 4 62 /26

3 255.255.255.224 8 30 /27

4 255.255.255.240 16 14 /28

5 255.255.255.248 32 6 /29

6 255.255.255.252 64 2 /30

Subnetting Example

The first entry in the Class A table (/10 subnet mask) borrows two bits (the leftmost bits) from the host portion of the network for subnetting, then with two bits you have four (2

2 ) combinations, 00, 01, 10, and 11. Each of these will

represent a subnet.

Binary Notation Decimal Notation

-------------------------------------------------- -----------------

xxxx xxxx. 0000 0000.0000 0000.0000 0000/10 ------> X.0.0.0/10

xxxx xxxx. 0100 0000.0000 0000.0000 0000/10 ------> X.64.0.0/10

xxxx xxxx. 1000 0000.0000 0000.0000 0000/10 ------> X.128.0.0/10

xxxx xxxx. 1100 0000.0000 0000.0000 0000/10 ------> X.192.0.0/10

Out of these four subnets, 00 and 11 are called subnet zero and the all-ones subnet, respectively. Prior to Cisco IOS

® Software Release 12.0, the ip subnet-zero global configuration command was required to be able to configure

subnet zero on an interface. In Cisco IOS 12.0, ip subnet-zero is enabled by default.

Note: The subnet zero and all-ones subnet are included in the effective number of subnets as shown in the third column.

Since the host portion has now lost two bits, the host portion will have only 22 bits (out of the last three octets). This means the complete Class A network is now divided (or subnetted) into four subnets, and each subnet can have 2

22 hosts (4194304). A host portion with all zeros is network number itself, and a host portion with all ones is reserved

for broadcast on that subnet, leaving the effective number of hosts to 4194302 (2 22

– 2), as shown in the fourth column.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f33.shtml#subnetting
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f33.shtml#subnetting
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f33.shtml#subnetting
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f33.shtml#subnetting
NW/Useful files/IPv6 Address structure.pdf
IPv6 Address structure Hexadecimal Number System Before introducing IPv6 Address format, we shall look into Hexadecimal Number System. Hexadecimal is positional number system which uses radix (base) of 16. To represent the values in readable format, this system uses 0-9 symbols to represent values from zero to nine and A-F symbol to represent values from ten to fifteen. Every digit in Hexadecimal can represent values from 0 to 15.

Address Structure An IPv6 address is made of 128 bits divided into eight 16-bits blocks. Each block is then converted into 4-digit Hexadecimal numbers separated by colon symbol.

For example, the below is 128 bit IPv6 address represented in binary format and divided into eight 16-bits blocks:

0010000000000001 0000000000000000 0011001000110100 1101111111100001 0000000001100011 0000000000000000 0000000000000000 1111111011111011

2001:0000:3238:DFE1:0063:0000:0000:FEFB

Rules to shorten the IPv6 address:

Even after converting into Hexadecimal format, IPv6 address remains long. IPv6 provides some rules to shorten the address. These rules are:

2001:0000:3238:DFE1:0063:0000:0000:FEFB

Rule:1 Discard leading Zero(es):

In Block 5, 0063, the leading two 0s can be omitted, such as (5th block):

2001:0000:3238:DFE1:63:0000:0000:FEFB

Rule:2 If two of more blocks contains consecutive zeroes, omit them all and replace with double colon sign ::, such as (6th and 7th block): 2001:0000:3238:DFE1:63::FEFB

Consecutive blocks of zeroes can be replaced only once by :: so if there are still blocks of zeroes in the address they can be shrink down to single zero, such as (2nd block):

2001:0:3238:DFE1:63::FEFB

Interface ID IPv6 has three different types of Unicast Address schemes.

The second half of the address (last 64 bits) is always used for Interface ID.

MAC address of a system is composed of 48-bits and represented in Hexadecimal. MAC address is considered to be uniquely assigned worldwide. Interface ID takes advantage of this uniqueness of MAC addresses. A host can auto-

-64) format.

First, a Host divides its own MAC address into two 24-bits halves. Then 16-bit Hex value 0xFFFE is sandwiched into those two halves of MAC address, resulting in 64-bit Interface ID.

Global Unicast Address

and uniquely addressable.

Global Routing Prefix: The most significant 48-bits are designated as Global Routing Prefix which is assigned to specific Autonomous System. Three most significant bits of Global Routing Prefix is always set to 001.

Link-Local Address Auto-configured IPv6 address is known as Link-Local address. This address always starts with FE80. First 16 bits of Link-Local address is always set to 1111 1110 1000 0000 (FE80). Next 48-bits are set to 0, thus:

Link-Local addresses are used for communication among IPv6 hosts on a link (broadcast segment) only. These addresses are not routable so a Router never forwards these addresses outside the link.

Unique-Local Address This type of IPv6 address which is though globally unique, but it should be used in local communication. This address has second half of Interface ID and first half is divided among Prefix, Local Bit, Global ID and Subnet ID.

Prefix is always set to 1111 110. L bit, which is set to 1 if the address is locally assigned. So far the meaning of L bit

SCOPE OF IPV6 UNICAST ADDRESSES:

The scope of Link-local address is limited to the segment.

Unique Local Address are boundary.

Global Unicast addresses are globally unique and recognizable.

NW/Useful files/IPv6 neighbor discovery.pdf
IPv6 neighbor discovery

Neighbor Discovery Protocol (NDP) itself does not describe a wire-level protocol or packet structure,

but rather it establishes directions for accomplishing routine tasks using certain algorithms and five

ICMPv6 message types.

Many of the capabilities provided by NDP are very similar to those found in IPv4's ARP and ICMPv4,

while others are new implementations available only under IPv6. RFC 4861 describes the nine

functions of NDP in detail.

Router Discovery

Whereas IPv4 hosts must rely on manual configuration or DHCP to provide the address of a default

gateway, IPv6 hosts can automatically locate default routers on the link. This is accomplished

through the use of two ICMPv6 messages: Router Solicitation (type 133) and Router

Advertisement (type 134). When first joining a link, an IPv6 host multicasts a router solicitation to

the all routers multicast group, and each router active on the link responds by sending a router

advertisement with its address to the all nodes group.

http://tools.ietf.org/html/rfc4861
Router advertisements indicate paths out of the local link, but they also specify additional information

necessary to assist other NDP operations.

Prefix Discovery

One of the options typically carried by a router advertisement is the Prefix Information option (type

3). Each prefix information option lists an IPv6 prefix (subnet) reachable on the local link. Remember

that it is not uncommon for multiple IPv6 prefixes to reside on the same link, and routers may include

more than one prefix in each advertisement. A host which knows what prefixes are reachable on the

link can communicate directly with destinations in those prefixes without passing its traffic through a

router.

Parameter Discovery

Another option included in router advertisements is the MTU option (type 5), which informs hosts of

the IP MTU to use. For example, this value is typically set to 1500 for Ethernet networks. However,

not all link types have a standardized MTU size. Including this option ensures all hosts know the

correct MTU to use.

Router advertisements also specify the default value hosts should use for the IPv6 hop count. This

isn't an option, but a field built into the router advertisement message header.

Address Autoconfiguration

NDP provides mechanisms for a host to automatically configure itself with an address from a prefix

learned from a local router through prefix discovery. This is done by concatenating a candidate

learned prefix with the EUI-64 address of the host's interface (embedding the MAC address inserting

FF:FE). In this manner, a host can achieve stateless autoconfiguration.

http://packetlife.net/blog/2008/aug/04/eui-64-ipv6/
Address Resolution

The function of address resolution was handled by ARP for IPv4, but is handled by ICMPv6 for IPv6.

In a process very similar to router discovery, two ICMPv6 messages are used: Neighbor

Solicitation (type 135) and Neighbor Advertisement (type 136). A host seeking the link layer

address of a neighbor multicasts a neighbor solicitation and the neighbor (if online) responds with its

link layer address in a neighbor advertisement.

Next-Hop Determination

As in IPv4, next-hop determination is simply a procedure for performing longest-match lookups on

the host routing table and, for off-link destinations, the selection of a default router.

Neighbor Unreachability Detection

NDP is able to determine the reachability of a neighbor by examining clues from upper-layer

protocols (for example, received TCP acknowledgments), or by actively re-performing address

resolution (via ICMPv6) when certain thresholds are reached.

Duplicate Address Detection

When a host first joins a link, it multicasts neighbor solicitations for its own IPv6 address for a short

period before attempting to use that address to communicate. If it receives a neighbor advertisement

in response, the host realizes that another neighbor on the link is already using that address. The

host will mark the address as a duplicate and will not use it on the link.

Note that this process is similar to IPv4 gratuitous ARP requests, but NDP elegantly allows for

detection of two hosts with the same address before both hosts are actively sending traffic from the

address.

Redirection

A fifth type of ICMPv6 message, the Redirect (type 137), is used by routers to either point hosts

toward a more preferable router, or to indicate that the destination actually resides on link. ICMPv4

provides the same capability with its own redirect message.

NW/Useful files/ipv6_reference_card.pdf
IPv6 Address Types

::/128

::1/128

::ffff/96

Example: ::ffff:192.0.2.47

fc00::/7

Example: fdf8:f53b:82e4::53

fe80::/10

Example: fe80::200:5aee:feaa:20a2

Prefix Designation and Explanation IPv4 Equivalent

Unspecified This address may only be used as a source address by an initialising host before it has learned its own address.

Loopback This address is used when a host talks to itself over IPv6. This often happens when one program sends data to another.

IPv4-Mapped These addresses are used to embed IPv4 addresses in an IPv6 address. One use for this is in a dual stack transition scenario where IPv4 addresses can be mapped into an IPv6 address. See RFC 4038 for more details.

Unique Local Addresses (ULAs) These addresses are reserved for local use in home and enterprise environments and are not public address space.

These addresses might not be unique, and there is no formal address registration. Packets with these addresses in the source or destination fields are not intended to be routed on the public Internet but are intended to be routed within the enterprise or organisation.

See RFC 4193 for more details.

Link-Local Addresses These addresses are used on a single link or a non-routed common access network, such as an Ethernet LAN. They do not need to be unique outside of that link.

Link-local addresses may appear as the source or destination of an IPv6 packet. Routers must not forward IPv6 packets if the source or destination contains a link- local address.

Link-local addresses may appear as the source or destination of an IPv6 packet. Routers must not forward IPv6 packets if the source or destination contains a link- local address.

0.0.0.0

127.0.0.1

There is no equivalent. However, the mapped IPv4 address can be looked up in the relevant RIR’s Whois database.

Private, or RFC 1918 address space:

10.0.0.0/8 172.16.0.0/12 192.168.0.0/16

169.254.0.0/16

This sheet is available at www.ripe.net/ipv6-address-types • Produced by the RIPE NCC in cooperation with ICANN • www.ripe.net • www.icann.org

IPv6 Address Types

2001:0000::/32

Example: 2001:0000:4136:e378: 8000:63bf:3fff:fdd2

2001:0002::/48

Example: 2001:0002:6c::430

2001:0010::/28

Example: 2001:10:240:ab::a

2002::/16

Example: 2002:cb0a:3cdd:1::1

2001:db8::/32

Example: 2001:db8:8:4::2

2000::/3

ff00::/8

Example: ff01:0:0:0:0:0:0:2

Prefix Designation and Explanation IPv4 Equivalent

Teredo This is a mapped address allowing IPv6 tunneling through IPv4 NATs. The address is formed using the Teredo prefix, the server’s unique IPv4 address, flags describing the type of NAT, the obfuscated client port and the client IPv4 address, which is probably a private address. It is possible to reverse the process and identify the IPv4 address of the relay server, which can then be looked up in the relevant RIR’s Whois database.

You can do this on the following webpage: http://www.potaroo.net/cgi-bin/ipv6addr

Benchmarking These addresses are reserved for use in documentation. They should not be used as source or destination addresses.

Orchid These addresses are used for a fixed-term experiment. They should only be visible on an end-to-end basis and routers should not see packets using them as source or destination addresses.

6to4 A 6to4 gateway adds its IPv4 address to this 2002::/16, creating a unique /48 prefix. As the IPv4 address of the gateway router is used to compose the IPv6 prefix, it is possible to reverse the process and identify the IPv4 address, which can then be looked up in the relevant RIR’s Whois database.

You can do this on the following webpage: http://www.potaroo.net/cgi-bin/ipv6addr

Documentation These addresses are used in examples and documentation. They should never be source or destination addresses.

Global Unicast Other than the exceptions documented in this table, the operators of networks using these addresses can be found using the Whois servers of the RIRs listed in the registry at: http://www.iana.org/assignments/ipv6- unicast-address-assignments

Multicast These addresses are used to identify multicast groups. They should only be used as destination addresses, never as source addresses.

No equivalent

198.18.0.0/15

No equivalent

There is no equivalent but 192.88.99.0/24 has been reserved as the 6to4 relay anycast address prefix by the IETF.

192.0.2.0/24 198.51.100.0/24 203.0.113.0/24

No equivalent single block

224.0.0.0/4

This sheet is available at www.ripe.net/ipv6-address-types • Produced by the RIPE NCC in cooperation with ICANN • www.ripe.net • www.icann.org

NW/Useful files/Lecture 4- Sub_Supernetting and Classless Addressing.pdf
©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200311

Chapter 5

Subnetting/Supernetting and

Classless Addressing

• SUBNETTING • SUPERNETTING • CLASSLESS ADDRSSING

©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200322

SUBNETTING5.15.1

©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200333

A network with two levels of hierarchy (not subnetted)

• All hosts in such a large network must be laid out as ONE physical network

• May not always be feasible (due to geographic constraints)

©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200344

A network with three levels of hierarchy (subnetted)

• 3-step delivery: site, subnet, host.

©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200355

Default mask and subnet mask

Subnetwork

©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200366

Finding the Subnet Address

Given an IP address, we can find the subnet address the same way we found the network address in the previous chapter. We apply the mask to the address. We can do this in two ways: straight or short-cut.

©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200377

Straight Method

In the straight method, we use binary notation for both the address and the mask and then apply the AND operation to find the subnet address.

Example 1Example 1

What is the subnetwork address if the destination address is 200.45.34.56 and the subnet mask is 255.255.240.0?

11001000 00101101 00100010 00111000

11111111 11111111 11110000 00000000

11001000 00101101 001000000000 0000000000000000

The subnetwork address is 200.45.32.0.

©The McGraw-Hill Companies, Inc., 2000 © Adapted for use at JMU by Mohamed Aboutabl, 200388

Short-Cut Method