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identified in several ways, including by a MAC (Media Access Control) address, an IP (Internet Protocol)
address, an IPX (Novell Netware) address, or perhaps a URL (Uniform Resource Locator).
Instant Answer One thing all network nodes have in common is that in order for their addresses to be
considered proper network addresses, they must have two parts present: a host address and a network address.
The host address portion identifies the individual node. The network address portion identifies the network or
network segment on which the host address can be found.
Time-Saver There are many network addressing schemes in use. For the CCNA exam, concentrate on the IP
addressing scheme. You also want to familiarize yourself with Novell Netware IPX addressing, and be
absolutely sure you understand MAC addresses in detail as well.
MAC addresses
In essence, a Media Access Control (MAC) address is the unique address of a network interface card (NIC).
This address is burned into the NIC circuit during manufacturing and is a unique number that solely identifies
each NIC. Every so often the system breaks down and NICs with duplicate MAC addresses are produced and
installed in the same network. The network addressing situation that could never happen does, with
136
predictably bad results. A MAC address is also referred to as a physical address or a burned-in address.
Remember MAC addresses, which are Data Link layer addresses, differ from Network layer addresses. MAC
addresses are flat addresses in that they identify only the node with which they are associated and have no
relationship to any other network elements. In many ways, Mac addresses are like a Social Security number
for NICs, identifying only one NIC at a time.
A MAC hex on you
Remember A MAC address consists of a 48-bit or 6-byte hexadecimal number. ItÇs represented in the form
of six two-digit numbers separated by dashes. The first 24 bits (3 bytes) of the MAC address contain a code
assigned by the IEEE (The Institute of Electrical and Electronics Engineers) to uniquely identify the
manufacturer of the card, and the 24 bits (3 bytes) are a number uniquely assigned by the manufacturer.
Figure 12-1 illustrates the MAC address and its parts.
Time-Saver On the test, youÇre not asked to convert hex to decimal or vice versa. So, donÇt waste your time
studying that mystery of the ages.
Figure 12-1: The MAC address and its parts.
Instant Answer Here are two points relating to MAC addresses that youÇre likely to see on
the test:
" ARP (Address Resolution Protocol): Uses broadcast messages to learn the MAC or Ethernet
address of a known IP address. The node with the broadcasted IP address responds with its MAC
address, completing the set.
"
Reverse ARP (RARP): Broadcasts messages to learn the IP address corresponding to a known MAC
address. This requires the presence of a RARP (pronounced Ýrarp,Û what else?) server on the
network. An example of where this procedure is used is booting a diskless workstation.
A Novell idea
Until Netware version 5, IPX was the default protocol for a Novell Netware network. You need to know IPX
networking fairly well for the CCNA exam, but you especially need to know about IPX and MAC addresses.
Instant Answer An IPX address is 10 bytes (80 bits) long. Four bytes (32 bits) is the network number and 6
bytes (48 bits) is the node number. If 48 bits sounds familiar, it should. The node number is normally the
MAC address of the node. Take our advice and memorize these numbers. HereÇs an example to help you
visualize this better:
Network address:4b2c
Node address:0000.06d2.ef67
137
In this example, the value 4b2c represents the network address. It could have been shown as 0000.4b2c, but
the leading zeros are usually left off. The remainder of the number is the node address. Its zeros are shown
because they occur in the middle of the IPX address.
Tip Remember that when you store a number in hexadecimal form, each byte (8 bits) holds two hex values.
For example, the hexadecimal value ÝFFÛ is stored in a single byte. Just for the sake of trivia, each
half-byte is called a nibble.
Remember Unlike IP addresses (see ÝWorking with IP addressesÛ later in this section), IPX addresses are
not structured into classes. ItÇs not uncommon for the network number not to use the entire 6 bytes. Any
zeros at the beginning of the network address are dropped.
Working with IP addresses
You can probably work with decimal numbers much easier than with the binary numbers needed by the
computer. It would be very awkward, not to mention time-consuming and error-prone, if humans had to
write out network addresses in binary representation. To avoid the inherent problems of humans and binary
numbers, the powers that be have devised a system to designate network numbers in decimal. Bless them!
Octets and quartets
Remember The 32-bit IP (Internet Protocol) address is broken up into four octets, which are arranged into a
dotted-decimal notation scheme. An octet is a set of 8 bits and not a musical instrument. WeÇre sure youÇve
seen an IP address somewhere in the past, but just in case, hereÇs an example of an IP address with its four
octets arranged into its dotted-decimal scheme:
172.64.126.52
This example is the type of addressing used in the current and predominant IP version 4. You wonÇt see IP
version 6 on the CCNA exam.
Thinking in binary
The binary system uses only two values (0 and 1) to represent numbers in positions representing increasing [ Pobierz całość w formacie PDF ]
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identified in several ways, including by a MAC (Media Access Control) address, an IP (Internet Protocol)
address, an IPX (Novell Netware) address, or perhaps a URL (Uniform Resource Locator).
Instant Answer One thing all network nodes have in common is that in order for their addresses to be
considered proper network addresses, they must have two parts present: a host address and a network address.
The host address portion identifies the individual node. The network address portion identifies the network or
network segment on which the host address can be found.
Time-Saver There are many network addressing schemes in use. For the CCNA exam, concentrate on the IP
addressing scheme. You also want to familiarize yourself with Novell Netware IPX addressing, and be
absolutely sure you understand MAC addresses in detail as well.
MAC addresses
In essence, a Media Access Control (MAC) address is the unique address of a network interface card (NIC).
This address is burned into the NIC circuit during manufacturing and is a unique number that solely identifies
each NIC. Every so often the system breaks down and NICs with duplicate MAC addresses are produced and
installed in the same network. The network addressing situation that could never happen does, with
136
predictably bad results. A MAC address is also referred to as a physical address or a burned-in address.
Remember MAC addresses, which are Data Link layer addresses, differ from Network layer addresses. MAC
addresses are flat addresses in that they identify only the node with which they are associated and have no
relationship to any other network elements. In many ways, Mac addresses are like a Social Security number
for NICs, identifying only one NIC at a time.
A MAC hex on you
Remember A MAC address consists of a 48-bit or 6-byte hexadecimal number. ItÇs represented in the form
of six two-digit numbers separated by dashes. The first 24 bits (3 bytes) of the MAC address contain a code
assigned by the IEEE (The Institute of Electrical and Electronics Engineers) to uniquely identify the
manufacturer of the card, and the 24 bits (3 bytes) are a number uniquely assigned by the manufacturer.
Figure 12-1 illustrates the MAC address and its parts.
Time-Saver On the test, youÇre not asked to convert hex to decimal or vice versa. So, donÇt waste your time
studying that mystery of the ages.
Figure 12-1: The MAC address and its parts.
Instant Answer Here are two points relating to MAC addresses that youÇre likely to see on
the test:
" ARP (Address Resolution Protocol): Uses broadcast messages to learn the MAC or Ethernet
address of a known IP address. The node with the broadcasted IP address responds with its MAC
address, completing the set.
"
Reverse ARP (RARP): Broadcasts messages to learn the IP address corresponding to a known MAC
address. This requires the presence of a RARP (pronounced Ýrarp,Û what else?) server on the
network. An example of where this procedure is used is booting a diskless workstation.
A Novell idea
Until Netware version 5, IPX was the default protocol for a Novell Netware network. You need to know IPX
networking fairly well for the CCNA exam, but you especially need to know about IPX and MAC addresses.
Instant Answer An IPX address is 10 bytes (80 bits) long. Four bytes (32 bits) is the network number and 6
bytes (48 bits) is the node number. If 48 bits sounds familiar, it should. The node number is normally the
MAC address of the node. Take our advice and memorize these numbers. HereÇs an example to help you
visualize this better:
Network address:4b2c
Node address:0000.06d2.ef67
137
In this example, the value 4b2c represents the network address. It could have been shown as 0000.4b2c, but
the leading zeros are usually left off. The remainder of the number is the node address. Its zeros are shown
because they occur in the middle of the IPX address.
Tip Remember that when you store a number in hexadecimal form, each byte (8 bits) holds two hex values.
For example, the hexadecimal value ÝFFÛ is stored in a single byte. Just for the sake of trivia, each
half-byte is called a nibble.
Remember Unlike IP addresses (see ÝWorking with IP addressesÛ later in this section), IPX addresses are
not structured into classes. ItÇs not uncommon for the network number not to use the entire 6 bytes. Any
zeros at the beginning of the network address are dropped.
Working with IP addresses
You can probably work with decimal numbers much easier than with the binary numbers needed by the
computer. It would be very awkward, not to mention time-consuming and error-prone, if humans had to
write out network addresses in binary representation. To avoid the inherent problems of humans and binary
numbers, the powers that be have devised a system to designate network numbers in decimal. Bless them!
Octets and quartets
Remember The 32-bit IP (Internet Protocol) address is broken up into four octets, which are arranged into a
dotted-decimal notation scheme. An octet is a set of 8 bits and not a musical instrument. WeÇre sure youÇve
seen an IP address somewhere in the past, but just in case, hereÇs an example of an IP address with its four
octets arranged into its dotted-decimal scheme:
172.64.126.52
This example is the type of addressing used in the current and predominant IP version 4. You wonÇt see IP
version 6 on the CCNA exam.
Thinking in binary
The binary system uses only two values (0 and 1) to represent numbers in positions representing increasing [ Pobierz całość w formacie PDF ]