IP Address Allocation
5-3
8000-A2-GB21-20
November 1997
Host Addressing
Host addresses within the service domain are assigned to end-user systems.
Because they are host addresses, they have a subnet mask of 255.255.255.255
and can be geographically dispersed. (When structured subnet addressing is
discussed in the next section, you will see how IP addresses are allocated to
certain areas.) This conserves address space, but may not scale well to large
numbers of end-user systems. Manual configuration is required for every host
address and routing performance may be decreased.
The following illustration is an example of host addressing.
97-15501-01
DSL Card
DSL Port 1
DSL Port 2
DSL Port 3
DSL Port 4
LAN Port
200.200.200.
n /
255.255.255.0
200.200.200.1 /
255.255.255.255
200.200.200.2 /
255.255.255.255
200.200.200.3 /
255.255.255.255
200.200.200.4 /
255.255.255.255
RTU1
RTU2
RTU3
RTU4
ES1
ES2
ES3
ES4
n = Any valid IP address
Structured Subnet Addressing
As an alternative to using host routes for end-user systems, structured subnetting
can be used. It scales better and performs better, but it does not allow
geographically dispersed subnets.
NOTE:
Structured subnetting is supported on the 8546 DSL card and the 5446 RTU.
It is not supported, however, on the 8540 DSL card and its corresponding
RTUs on the DSL ports.
Structured subnet addressing uses the following method:
Within the service domain, the NSP would provision a subnet of its domain to
a DSL card and all devices behind it.
The NSP would further subdivide that subnet into four additional subnets
(one behind each DSL port).
