There are a few special IP addresses on the Internet which are used . only under special circumstances:
The limited-broadcast IP address.
The limited-broadcast IP address is 255.255.255.255. This special IP address is most commonly used during system setup, when the system has little idea about its own IP address and subnet address. It is also seen quite often in the routing tables of various systems. Keeping in mind IP routing, packets addressed to this address are never forwarded by routers.
The network-directed broadcast IP address.
This special IP address has the host part made up of all 255s, with its network part the same as that of the network to which it is applicable. A typical example is 202.255.255.255, where the network part of the , IP address is 202 and the remaining part is the host-address part. Routers usually forward packets addressed to a network-directed I broadcast address.
The subnet-directed broadcast IP address.
In such an IP address, the host part of the address is represented by 255s, whereas the subnet part of the address stands for an actual subnet.
All-subnets-directed broadcast IP addIess.
Here, both the host and the subnet part of the address are represented by 255s. The subnet mask of the network must be known wherever such an address is being used.
The loopback IP address.
This special IP address stands for the localhost system. A packet addressed to the loopback address is actually addressed to the same local machine from which it originated. In effect, both the source and destination IP addresses point to the same system, though their values might be different. All loopback addresses must have the network part as 127; ; the most commonly used loopback address is 127.0.0.1.
The zeros IP address.
Typically, the 0.0.0.0 IP address is used as the zeros IP address. Such an IP address is mostly seen in a system's log files. If you see packets being sent from the zeros IP address, it means that an attacker is trying to fingerprint the target system (that is, the system where the log files were examined).