Lucent Technologies 6000 - Manual (Page 376)

9-12 MAX 6000/3000 Network Configuration Guide
Configuring IP Routing
Configuring system-level routing policies
The address pool parameters enable the MAX unit to assign an IP address to incoming calls
that are configured for dynamic assignment. These addresses are assigned on a first-come,
first-served basis. After the unit terminates a connection, its address is freed up and returned to
the pool for reassignment to another connection. Figure 9-7 shows a host using PPP dial-in
software to connect to the unit.
Figure 9-7. Address assigned dynamically from a pool
This example shows how to set up network-aligned address pools and use route
summarization.
Following are the rules for network-aligned address pools:
• The Pool#N Start address must be the first host address.
Subtract one from the Pool#N Start address for the base address for the subnet.
• The Pool#N Count value must be two less than the total number of addresses in the pool.
Add two to Pool#N Count for the total number of addresses in the subnet, and calculate the
mask for the subnet on the basis of this total.
For example, the following configuration is network aligned:
Ethernet
Mod Config
WAN options...
Pool#1 start=10.12.253.1
Pool#1 count=62
Pool#1 name=Engineering Dept.
Pool Summary=Yes
Pool#1 Start is set to 10.12.253.1. When you subtract one from this address, you get
10.12.253.0, which is a valid base address for a subnet defined by a mask of 255.255.255.192.
Note that 10.12.253.64, 10.12.253.128, and 10.12.253.192 are also valid zero addresses for the
same mask. The resulting address pool subnet is 10.12.253.0/26.
Pool#1 Count is set to 62. When you add two to the value of Pool#1 Count, you get 64. The
subnet mask for 64 addresses is 255.255.255.192 (256–64=192). The subnet notation for a
255.255.255.192 mask is /26.
After verifying that every one of the configured address pools is network-aligned, you must
enter a static route for each of them. These static routes handle all IP address that have not been
given to users, by routing them to the reject interface or the black-hole interface (which are
defined in “MAX IP interfaces” on page 9-4).
Note: The MAX unit creates a host route for every address assigned from the pools, and host
routes override subnet routes. Therefore, packets whose destination matches an assigned IP
address from the pool are properly routed and not discarded or bounced. Because the unit
MAX
IP Adrs=10.2.3.1/24
Pool#1 Start=10.2.3.200
Pool#1 Count=55
=10.2.3.212/32
Modem
WAN