Configuring the Shelf Controller
Providing a basic system IP configuration
APX 1000™ Getting Started Guide
5-9
192.32.8.0/30 was illegal because it had the same base address as the class C network
192.32.8.0/24, while the subnet 192.32.8.4/30 was legal. Modern implementations of TCP/IP
support zero subnets, and the APX 1000 implementation of the routing information protocol
(RIP) treats these subnets like any other network.
Table 5-2 shows subnet masks and prefix lengths for a class C network.
The broadcast address of any subnet has the host portion of the IP address set to all 1s (ones).
The network address (or base address) represents the network itself, because the host portion
of the IP address is all 0s (zeros). For example, supposing that the APX 1000 configuration
assigns the following address to a remote router:
198.5.248.120/29
The Ethernet network attached to that router has the following address range:
198.5.248.120 — 198.5.248.127
A host route is a special-case IP address with a prefix length of /32. For example:
198.5.248.40/32
Host routes are routes to a single host, rather than to a network or subnet. A 32-bit netmask
does not allow for any host addresses on the network, other than the single address that is
specified. It is, in effect, a one-address subnet.
Table 5-2. Decimal subnet masks and prefix lengths
Subnet mask
(dotted-decimal
notation)
Number of host addresses
Subnet
mask
(CIDR
notation)
255.255.255.0
254 hosts + 1 broadcast address, 1 network base address
/24
255.255.255.128
126 hosts + 1 broadcast address, 1 network base address
/25
255.255.255.192
62 hosts + 1 broadcast address, 1 network base address
/26
255.255.255.224
30 hosts + 1 broadcast address, 1 network base address
/27
255.255.255.240
14 hosts + 1 broadcast address, 1 network base address
/28
255.255.255.248
6 hosts + 1 broadcast address, 1 network base address
/29
255.255.255.252
2 hosts + 1 broadcast address, 1 network base address
/30
255.255.255.254
invalid mask (no hosts)
/31
255.255.255.255
1 host—a host route
/32