Black Box LPB724A, LPB716A, LPB708A, 8-/16-/24-Port 10/100 PoE PSE Web Smart Switch Default Gateway

8-/16-/24-Port 10/100 PoE PSE Web Smart Switch

we divide it into smaller networks by extending the network prefix from 16 bits to, say 24 bits, the network uses its third byte to subnet this class B network. The subnet mask is 255.255.255.0; each bit of the first three bytes is 1. The first two bytes are used to identify the class B network, the third byte is used to identify the subnet within this class B network, and the last byte is the host number.

Not all IP addresses are available in the subnetted network. Two special addresses are reserved. They are the addresses with all zeros and all ones host number.

As shown in the table below, the subnet mask with a 25-bit long, 255.255.255.128 address contains 126 members in the subnetted network. The network prefix length equals the bit number with 1s in that subnet mask. Use this table to count the number of IP addresses matched.

	Table 6-2. Subnet mask values.
Prefix Length	Number of IPs Matched	Number of Addressable IPs
/32	1	-
/31	2	-
/30	4	2
/29	8	6
/28	16	14
/27	32	30
/26	64	62
/25	128	126
/24	256	254
/23	512	510
/22	1024	1022
/21	2048	2046
/20	4096	4094
/19	8192	8190
/18	16384	16382
/17	32768	32766
/16	65536	65534

According to the scheme above, a subnet mask 255.255.255.0 will partition a network with the class C. It means that a maximum of 254 effective nodes will exist in this sub-netted network and is considered a physical network in an autonomous network. So it owns a network IP address such as 168.1.2.0.

With the subnet mask, a bigger network can be cut into small pieces of network. If we want to have more than two independent networks in a worknet, a partition to the network must be performed. In this case, subnet mask must be applied.

For different network applications, the subnet mask may be 255.255.255.240. This means it is a small network accommodating a maximum of 15 nodes in the network.

6.3 Default Gateway

For the routed packet, if the destination is not in the routing table, all the traffic is put into the device with the designated IP address, known as default router. Basically, it is a routing policy. The gateway setting is used for Trap Events Host only in the switch.

To assign an IP address to the switch, you just have to check what the IP address of the network is that will be connected to the switch. Use the same network address and append your host address to it.

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