Configuring IP Routing
Configuring system-level routing policies
MAX 6000/3000 Network Configuration Guide 9-11
Forcing callers configured for a pool address to accept dynamic assignment
During PPP negotiation, a caller can reject the IP address offered by the MAX unit and present
its own IP address for consideration. Connection profiles compare IP addresses as part of
authentication, so the unit would automatically reject such a request if the caller has a
Connection profile. Names/Passwords profiles have no such authentication mechanism,
however, and could potentially enable a caller to spoof a local address. You can set the Pool
Only parameter to instruct the MAX unit to hang up if a caller rejects the dynamic assignment.
Summarizing host routes in routing table advertisements
IP addresses assigned dynamically from a pool are added to the routing table as individual host
routes. You can summarize this network (the entire pool), cutting down significantly on route
flappage and the size of routing table advertisements.
The Pool Summary parameter enables or disables route summarization, which summarizes the
series of host routes in the pool into a single network route advertisement. The MAX unit
routes packets destined for a valid host address on the summarized network to the host, and the
MAX rejects packets destined for an invalid host address with an ICMP host unreachable
message.
To use the pool summary feature, you must set the Pool Summary parameter to Yes and create
a network-aligned pool.
To create a network-aligned pool, set the Pool #N Start parameter to specify the first host
address. Subtract one from the Pool #N Start setting to determine the network address (the zero
address on the subnet). The first and last address of a subnet are reserved, so you must set the
Pool #N Count parameter to specify a value that is two less than a power of two. For examp le,
you can use values 2, 6, 14, 30, 62, 126 or 254. The subnet mask includes a value that is two
greater than the Pool #N Count value. For example, with the following configuration:
Pool Summary=Yes
Pool#1 Start=10.12.253.1
Pool#1 Count=126
the network alignment address is (Pool #1 Start–1) 10.12.253.0 and the subnet mask is
(Pool #1 Count +2 addresses) 255.255.255.128. The resulting address-pool network is
10.12.253.0/25.
After you verify that every configured address pool is network-aligned, you must enter a st atic
route for each one.
If you do not use the pool summary feature, each address in a pool is advertised as a ho st rou t e
with a subnet mask of /32. In that case, the pool does not have to be network aligned, so any
IP address that begins a block of free addresses can serve as a pool base address.
Example of how to set up address pools with route summarization
This example shows how to set up network-aligned address pools and use route
summarization. It also shows how to enter a static route for the pool subnet and make the
Connection profile route private, both of which are requirements when using route
summarization.