IP Address Requirements

How Network Addresses Are Assigned

Network IDs are assigned by the NIC (Network Information Center). The network portion (first two bytes) of the class B address in the example above would be acquired from the NIC by a network administrator to avoid conflicts with other networks. The network administrator is then free to allocate subnets as needed since subnetting is not visible outside the network.

If you do not know the IP address the test set and/or DUT should be set to, or which unique host IDs are available, you should contact your network administrator.

How to Interpret IP Addresses

The network portion of the LAN IP Address depends on the address classification as shown below:

LAN IP Address Classification

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

An IP Address 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.

   

NOTE

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.

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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 IP Address Formatting .

IP Address Formatting

Class	Byte 1	Byte 2	Byte 3	Byte 4
A	Network	Host
B	Network		Host
C	Network			Host
D	Multicast

Determining the Test Set's Network Address

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. See Applying the Subnet Address .

Applying the Subnet Address

LAN IP Address	130								29								183								121
Subnet Mask	255								255								255								0
Subnet Mask (Binary)	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	0	0	0	0	0	0	0	0
LAN IP Address (Binary)	1	0	0	0	0	0	1	0	0	0	0	1	1	1	0	1	1	0	1	1	0	1	1	1	0	1	1	1	1	0	0	1
Subnet Address (Binary)	1	0	0	0	0	0	1	0	0	0	0	1	1	1	0	1	1	0	1	1	0	1	1	1	0	0	0	0	0	0	0	0
Subnet Address	Network130								Network 29								Subnet 183								Host 0

As shown in the table above, 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.

In this example the DUT IP Address would need to be set to 130.29.183.XXX to match the test set's subnet ID. The host portion of the LAN IP Address is identified by the bits corresponding to the 0 bits in the Subnet Mask. Therefore, the last byte in the DUT IP Address must not be 121 or any address that corresponds with any other host on the subnet at 130.29.183.XXX

This setting is non-volatile (it persists across partial and full presets and power-cycling the test set).