Network Management

• Subnet Mask

Subnet mask is used to determine the network and host portions of the address. Devices that belong to same network have the same network portion. Network portion of subnet mask contains sequence of ones and host portion contains zeros. Identifying the network and host portion is achieved by using AND operation.

Ping command is used to test the connectivity to another host in order to do that an echo request is sent to host address. Ping has a timeout value for reply. Ping can be used to test the configuration of local host by pinging 127.0.0.1 for IPv4 (::1 for IPv6). The response comes from network layer so it tests IP down through the network layer. It can also be used to test the connectivity to local LAN. Gateaway address is used to test and if its not responding a ping can be sent to another host on the same network. Another usage of ping is to test the ability of local host to communicate through a internetwork. Local host can ping an IPv4 host of a remote network.

Ping does not provide information about middle devices between the hosts. Traceroute generates a list of hops it is useful for troubleshooting. Round trip time(RTT) determines whether a hop fails to respond or not.

• Subnetting IP Networks

Subnetting is the process of creating smaller broadcast domains to decrease the size of the network. By subnetting prefix length is increased(/16 to /24). Host bits are borrowed to create more subnets. The first two octetes define the network portion and last two ones are for host IP addresses(e.g. 10.x.0.0/16).

subnetting /16

To avoid wasting addresses variable length subnet mask(VLSM) or subnetting a subnet can be applied. VLSM allows a network space to be consist of unequal portions. It helps to conserve IPv4 addresses. However, IPv6 is not concerned about this issue.

Cisco CCNA study materials were used as a source.