Cisco 10000 - Manual (Page 274)

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Cisco 10000 Series Router Software Configuration Guide
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Chapter 10 Configuring Address Pools
On-Demand Address Pool Manager
Limitations of DHCP-Based Address Assignment
DHCP-based address assignment has route summarization problems similar to the problems encountered
with RADIUS-based address assignment. Route summarization becomes less efficient as remote users
log on and off, and users have limited connectivity while BGP updates all of the PE routers with newly
configured routes.
For more information, see the “RADIUS-Based Address Assignment” section on page 10-2 .
On-Demand Address Pool Manager
The On-demand Address Pool Manager feature is a mechanism for assigning and managing IP addresses.
On-demand address pools (ODAPs) use a central server to manage a block of addresses for each
customer. The central server can be a Dynamic Host Configuration Protocol (DHCP) server or a
RADIUS server. After the ODAP is configured, the central server populates the ODAP with one or more
subnets leased from the central server. The central server divides each address pool into subnets and
assigns the subnets to PE routers upon request.
Note The Cisco Network Registrar (CNR) DHCP server and the Cisco Access Registrar (CAR) RADIUS
server support ODAPs.
The customer site connects to a provider edge (PE) router in the provider network. When an ODAP is
configured, the pool manager for the PE router initiates a request to the central server for an initial subnet
for a specific ODAP. The pool manager then monitors the utilization of the ODAP.
If the utilization of the pool exceeds a high-utilization threshold (high-utilization mark), the pool
manager requests an additional subnet from the central server and adds it to the ODAP. Similarly, if the
utilization of the pool decreases below the low-utilization threshold (low-utilization mark), the pool
manager returns one or more subnets to the central server from which it was originally leased. Each time
subnets are added to or removed from the ODAP, the summarized routes for each leased subnet must be
inserted or removed from the corresponding VRF.
The On-demand Address Pool Manager feature is described in the following topics:
• Feature History for On-Demand Address Pool Manager, page 10-5
• Address Allocation for PPP Sessions, page 10-5
• Subnet Releasing, page 10-5
• On-Demand Address Pools for MPLS VPNs, page 10-5
• Benefits On-Demand Address Pool Manager, page 10-6
• Prerequisites for On-Demand Address Pool Manager, page 10-6
• Required Configuration Tasks for On-Demand Address Pool Manager, page 10-6
• Optional Configuration Tasks for On-Demand Address Pool Manager, page 10-10
• Verifying On-Demand Address Pool Operation, page 10-12
• Configuration Examples for On-Demand Address Pool Manager, page 10-14
• Monitoring and Maintaining an On-Demand Address Pool, page 10-15