Subnet Masking:Like IP addresses, a subnet mask contains four bytes (32 bits) and is often written using the same "dotted-decimal" notation.
A subnet mask is different from an IP address, and it doesn't exist independently from the IP address. Instead, subnet masks accompany an IP address and the two values work together. Applying the subnet mask to an IP address splits the address into two parts, an "extended network address" and a host address. If we don't specify a subnet along with an IP address, usually the default subnet mask is assumed.
The default subnet masks for various classes of IP addresses are given below:
Class A: 255.0.0.0
Class B: 255.255.0.0
Class C: 255.255.255.0
The IP address and default gateway on a computer should be in the same network (or subnet). By following this rule one of the two given addresses (18.104.22.168 or 22.214.171.124) is a default gateway. However, the address 126.96.36.199 is a broadcast address and could not qualify for a default gateway. That leaves us with only one option.
An IP address is considered private if the IP number falls within one of the IP address ranges reserved for private uses by Internet standards groups. These private IP address ranges exist:
10.0.0.0 through 10.255.255.255
172.16.0.0 through 172.31.255.255
192.168.0.0 through 192.168.255.255
Private IP addresses are typically used on local networks including home, school and business LANs including airports and hotels.
TCP and UDP ports, protocols and their purpose. Some important port numbers are as given below
21 - FTP (File Transfer Protocol)
22 - SSH (Secure Shell)
25 - SMTP (Simple Mail Transfer Protocol)
80 - HTTP (Hypertext Transfer Protocol)/WWW
143 - IMAP (Internet Message Access Protocol
443 - HTTPS (Hyper Text Transfer Protocol Secure)
802.11 standards: 802.11a standard provides wireless LAN bandwidth of up to 54Mbps in the 5GHz frequency spectrum. The 802.11a standard also uses orthogonal frequency division multiplexing (OFDM) for encoding rather than FHSS or DSSS.802.11a is not compatible. Bluetooth is entirely a different protocol standard.
802.11b standard provides for bandwidths of up to 11 Mbps (with fallback rates of 5.5, 2, and 1 Mbps) in the 2.4G Hz frequency spectrum. This standard is also called Wi-Fi or 802.11 high rates. The 802.11b standard uses only DSSS for data encoding.802.11b is compatible with 802.11g.
802.11g standard provides for bandwidths of 20 Mbps+ in the 2.4 GHz frequency spectrum. This offers a maximum rate of 54 Mbps and is backward compatible with 802.11b.
802.11n the newest of the wireless standards you need to know for the exam is 802.11n. The goal of the 802.11n standard is to significantly increase throughput in both the 2.4 GHz and the 5 GHz frequency range. The baseline goal of the standard was to reach speeds of 100 Mbps, but given the right conditions, it is estimated that the 802.11n speeds might be able to reach 600 Mbps. In practical operation, 802.11n speeds will be much slower.