Address reservation for sticky leases adds support in local DHCP servers to provide IP address reservation for the assignment of sticky leases. These leases are pre-provisioned in the server (by SNMP or CLI) with a specific set of user-identification parameters. This set of parameters must be unique for each pool to avoid duplicate leases. For management purposes, these leases also have an additional hostname parameter to easily retrieve them by SNMP. When a sticky lease is created, the corresponding requested IP address is allocated from the specified pool and this address afterwards can only be used by DHCP if they match the specified user identification parameters. It is not possible to make an existing DHCP lease sticky.
Sticky leases are persistent but not synchronized in multi-chassis synchronization. To support multi-chassis redundancy, a management system can allocate the lease on one 7750 SR, immediately retrieve the lease and populate it again on the redundant router. For this to work, sticky leases should not be combined with any other allocation method (for example, regular DHCP leases, or Local Address Assignment because these methods can already allocate the address on the standby node).
This feature targets two scenarios:
simplified IP address reservation
It is not necessary to provision LUDB entries and exclude ranges for sticky leases. After the lease is reserved in the local DHCP server (triggered by an external system by SNMP or CLI), the external system can then subsequently assign the corresponding IP address to a DHCP client that matches the configured lease. A use case of this related to virtual residential gateway (vRGW) application and is described in the vRGW section.
pool management without DHCP
In pure management cases, this provides an easy method to perform pool management without implementing DHCP-specific configurations. For example, a management platform can allocate an IP address from a pool using the sticky lease mechanism and then assign this to a static host without risking overlap.