Typically, the local address server allocates IP addresses from a pool of addresses that is stored locally on the router. However, shared local address pools enable a local address server to hand out addresses that are allocated from DHCP local server address pools within the same virtual router. The addresses are configured and managed within DHCP. Therefore, thresholds are not configured on the shared pool, but are instead managed by the referenced DHCP local server pool.
A shared local address pool references one DHCP address pool. The shared local address pool can then obtain addresses from the referenced DHCP address pool and from any DHCP address pools that are linked to the referenced DHCP address pool.
Figure 2 illustrates a shared local address pool environment that includes four linked DHCP address pools. In the figure, both Shared_LAS_Pool_A and Shared_LAS_Pool_B reference DHCP_Pool_1, and can therefore obtain addresses from all four DHCP address pools. Shared_LAS_Pool_C references DHCP_Pool_3 and can get addresses from DHCP_Pool_3 and DHCP_Pool_4.
Figure 2: Shared Local Address Pools
When the local address server requests an address from a shared address pool, the address is returned from the referenced DHCP pool or a subsequent linked pool. If no address is available, DHCP notifies the local address server and the search is ended.
Keep the following guidelines in mind when using shared local address pools:
Example
This following commands create the shared address pools in Figure 2:
- host1(config)#ip local shared-pool Shared_LAS_Pool_A
DHCP_Pool_1
- host1(config)#ip local shared-pool Shared_LAS_Pool_B
DHCP_Pool_1
- host1(config)#ip local shared-pool Shared_LAS_Pool_C
DHCP_Pool_3
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