Cisco 10000-2P2-2DC Software Guide - Page 277

Chapter 10 Configuring Address Pools On-Demand Address Pool Manager Feature History for On-Demand Address Pool Manager Cisco IOS Release 12.2(15)BX 12.3(7)XI1 12.2(28)SB Description This feature was introduced on the Cisco 10000 series router. This feature was integrated into Cisco IOS Release 12.3(7)XI1. This feature was integrated into Cisco IOS Release 12.2(28)SB. Required PRE PRE2 PRE2 PRE2 Address Allocation for PPP Sessions For individual address allocation for PPP sessions, the pool manager searches for a free address beginning with the very first leased subnet. If a free address is not available in the first subnet, the pool manager searches the second leased subnet, and so on until a free address is found. This method of address allocation allows for efficient subnet release and route summarization. However, it differs from the normal DHCP address selection policy in which the IP address of the receiving interface is taken into account. The on-demand address pool manager feature provides an IP address pooling mechanism for PPP that allows the DHCP server to distinguish between a normal DHCP address request and an address request for a PPP client. Subnet Releasing The pool manager releases subnets beginning with the last leased subnet. The pool manager searches for a releasable subnet-a subnet with no addresses currently being leased. If it finds a releasable subnet, it releases the subnet and removes the summarized route for that subnet. If more than one releasable subnet exists, the pool manager releases the most recently allocated subnet. The pool manager takes no action if it does not find a releasable subnet. If the high utilization mark is reached by releasing the subnet, the pool manager does not release the subnet. Regardless of the instantaneous utilization level, the pool manager never releases the first leased subnet until it disables the ODAP. On-Demand Address Pools for MPLS VPNs The on-demand address pool manager feature provides support for Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) environments. This feature automates the resizing of address pools, reducing network loading and manual configuration. Each ODAP is configured and associated with a specific MPLS VPN. Each VPN is associated with one or more VRFs. The VRF maintains a routing table and other information associated with a specific customer VPN site. The utilization of the on-demand address pool occurs as described in the "On-Demand Address Pool Manager" section on page 10-4, except that address allocation occurs within the VRF associated with a particular VPN. Only the ODAP associated with a specific VPN can allocate addresses to PPP sessions belonging to that VPN. The PE router on which the ODAP is configured terminates the PPP sessions and maps the remote user to the corresponding MPLS VPNs. OL-2226-23 Cisco 10000 Series Router Software Configuration Guide 10-5