Lucent Technologies 6000 User Manual

MAX 6000/3000 Network Configuration Guide

 9-3

The broadcast address of any subnet has the host portion of the IP address set to all ones. The 
network address (or base address) represents the network itself, because the host portion of the 
IP address is all zeros. For example, if the MAX assigns the following address to a remote 
router:

IP address=198.5.248.120/29

The Ethernet attached to that router has the following address range: 

198.5.248.120 — 198.5.248.127

in which 

198.5.248.120

 is a network (base) address and 

198.5.248.127 

is a broadcast 

address.

A host route is a special-case IP address with a subnet mask of /32. Host routes are required for 
dial-in hosts. For example:

198.5.248.40/32

Table 9-2 shows standard subnet masks for a class C network and the subnet notation. 

Early implementations of TCP/IP do not allow zero subnets, that is, subnetwork addresses in 
which the last octet is zero. As a result, in early TCP/IP implementation, subnetworks are not 
permitted to have the same base address that a class A, B, or C network would have. Lucent’s 
implementation of RIP 2 and OSPF, like other modern implementations of TCP/IP, treat zero 
subnetworks as they would any other network. 

You should decide whether to support and configure zero subnetworks for your environment. 
If you configure them in some cases and treat them as unsupported in other cases, you will 
encounter routing problems.

255.255.255.0

254 hosts + 1 broadcast, 1 network (base)

/24

255.255.255.128

126 hosts + 1 broadcast, 1 network (base)

/25

255.255.255.192

62 hosts + 1 broadcast, 1 network (base)

/26

255.255.255.224

30 hosts + 1 broadcast, 1 network (base)

/27

255.255.255.240

14 hosts + 1 broadcast, 1 network (base)

/28

255.255.255.248

6 hosts + 1 broadcast, 1 network (base)

/29

255.255.255.252

2 hosts + 1 broadcast, 1 network (base)

/30

255.255.255.254

invalid subnet mask (no hosts)

/31

255.255.255.255

1 host—a host route

/32