Switch User Manual

IP routing 15

A subnet address is created by increasing the network portion to include

a subnet address, thus decreasing the host portion of the IP address. For

example, in the address 128.32.10.0, the network portion is 128.32, while

the subnet is found in the ﬁrst octet of the host portion (10). A subnet mask

is applied to the IP address and identiﬁes the network and host portions

of the address.

" Subnet masks for Class B and Class C IP addresses" (page 15)illustrates

how subnet masks used with Class B and Class C addresses can create

differing numbers of subnets and hosts. This example shows the use of the

zero subnet, which is permitted on a Nortel Ethernet Routing Switch 5510.

Subnet masks for Class B and Class C IP addresses

Number

of bits

Subnet Mask

Number of Subnets

(Recommended)

Number of Hosts

per Subnet

Class B

2 255.255.192.0 2 16 382

3 255.255.224.0 6 8 190

4 255.255.240.0 14 4 094

255.255.248.0 30 2 046

6 255.255.252.0 62 1 022

255.255.254.0 126 510

8 255.255.255.0 254 254

9 255.255.255.128 510 126

10 255.255.255.192 1 022 62

11 255.255.255.224 2 046 30

12 255.255.255.240 4 094 14

13 255.255.255.248 8 190 6

14 255.255.255.252 16 382 2

Class C

1 255.255.255.128 0 126

2 255.255.255.192 2 62

3 255.255.255.224 6 30

4 255.255.255.240 14 14

255.255.255.248 30 6

6 255.255.255.252 62 2

Nortel Ethernet Routing Switch 5500 Series

Conﬁguration-IP Routing Protocols

NN47200-503 03.01 Standard

5.1 27 August 2007