The test set does not allow LAN IP Addresses in the range of 127.0.0.0 to 127.255.255.255 because these addresses are assigned for use as the Internet host loopback address.
Last updated: 2014-11-28
An IP Address (the IP address defaults for IPv4 address if there is no specified statements) consists of a 4-byte (32 bit) number. Each byte is in a decimal form separated from other bytes by a dot. This is referred to as a "dotted decimal" format.
The network portion of the LAN IP Address depends on the address classification as shown below:
Class A = 1.0.0.0 to 127.255.255.255
Class B = 128.0.0.0 to 191.255.255.255
Class C = 192.0.0.0 to 223.255.255.255
Class D = 224.0.0.0 to 247.255.255.255
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The test set does not allow LAN IP Addresses in the range of 127.0.0.0 to 127.255.255.255 because these addresses are assigned for use as the Internet host loopback address. |
The IP address class defines which bytes contain the network portion of the address. For Class A addresses, the first byte from the left identifies the network. For class B it is the first two bytes from the left, and for class C it is the first three bytes. Class D addresses are multicast, which are used when a datagram is directed to multiple hosts. See the following table.
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Class |
Byte 1 |
Byte 2 |
Byte 3 |
Byte 4 |
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A |
Network |
Host |
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B |
Network |
Host |
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C |
Network |
Host |
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D |
Multicast |
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If the test set's LAN IP Address is set to 130.29.183.121, as shown below, the first two bytes represent the network portion since this is a Class B address.
If the test set is on a subnet, the Subnet Mask must be applied to determine the subnet address. This is done by performing bit-wise AND logic between the binary values of the LAN IP Address and Subnet Mask.
The Subnet Mask splits the 16 bit host portion of the class B address into an 8-bit subnet ID and an 8-bit host ID.
This setting is non-volatile (it persists across partial and full presets and power-cycling the test set).
IP version 4 (known as IPv4) has been widely used for decades of years and it is proven to be robust, easily implemented and interoperable. However, as the increasingly growth of the internet, IPv4 faces many problems: the impending exhaustion address space, large routing tables etc. IP version 6 (known as IPv6) is developed by Internet Engineering Task Force (IETF) to solve these problems.
IPv6 addresses are 128-bit identifiers for interfaces and sets of interfaces. These 128 bit is divided to eight 16-bit blocks with each block is represented by a 4-digital hexadecimal number and separated by colons. For example: 2001:0DB8:0000:2F3B:02AA:00FF:FE28:9C5A. Uppercase or lower case is not sensitive for IPv6 addresses.
For the IPv6 addresses with long sequences of `0', double-colon "::" is used to compress the `0's in the contiguous sequence of 16-bit block to further simplify the representation. "::" indicates one or more groups of 16 bits of `0's and can also be used at the leading or trailing part of an address. For example: FE80:0:0:0:2AA:FF:FE9A:4CA2 can be further simplified by `0' compressing and turns to: FE80::2AA:FF:FE9A:4CA2.
The following formula can be used if you want to determine how many `0's are represented by the "::" :
the number of bits expressed by "::" = (8-number of blocks in the address)*16.
For example: in the address FE80::2AA:FF:FE9A:4CA2, there are 5 blocks. The number of bits expressed by the "::" is 48 (i.e. (8-5)*16=48).
Note that this compression can only appear once in a given IPv6 address, or you could not determine how many `0's are represented by each instance of "::".
When dealing with a mixed environment of IPv4 and IPv6 nodes, x:x:x:x:x:x:d.d.d.d can be used as a more convenient form, where the 'x's are the hexadecimal values of the six high-order 16-bit pieces of the address, and the 'd's are the decimal values of the four low-order 8-bit pieces of the address (standard IPv4 representation). For example: "0:0:0:0:0:FFFF:129.144.52.38" and the compressed form "::FFFF:129.144.52.38" are all valid addresses.
An IPv6 address is comprised of two portion: IPv6 Prefix and IPv6 interface ID.
An IPv6 prefix indicates the block of address space or a network. The IPv6 prefix follows the general IPv6 addressing rules and is represented as: IPv6 address/prefix length.
Where IPv6 address represents the hexadecimal 128-bit address, and prefix length is a decimal value that indicates the number of contiguous, higher-order bits of the address that make up the network portion of the address. For example, "21DA:D3::/48" and "21DA:D3:0:2F3B::/64" are IPv6 address prefixes.
IPv6 Interface ID indicates the specific interface which is unique to the IPv6 prefix of the IPv6 address.
In general, there are three types of IPv6 address: Unicast IPv6 Addresses, Multicast IPv6 Addresses and Anycast IPv6 Addresses.
An unicast address identifies a single interface within the scope of the type of unicast address. A packet sent to a unicast address is delivered to the interface identified by that address.
For the Unicast IPv6 Addresses, there are many types: Global unicast addresses, Link local addresses etc. Global unicast addresses are globally routable and reachable on the IPv6 portion of the Internet.
A prefix for link local addresses is always FE80::/64 with the interface ID be 64-bit length.
A multicast address identifies multiple interfaces (typically belonging to different nodes). A packet sent to a multicast address is delivered to all interfaces identified by that address.
An anycast address identifies a set of interfaces (typically belonging to different nodes). A packet sent to an anycast address is delivered to one of the interfaces identified by that address.