A high rate of DHCP renewals can create a load on the compact flash file system when subscriber management and DHCP server persistence is enabled. To optimize the access to the Dynamic Data Persistency (DDP) files on the compact flash, a lease-time threshold can be specified that controls the eligibility of a DHCP lease for persistency updates when no other data other than the lease expiry time is to be updated.
configure
system
persistence
subscriber-mgmt
location cf2:
exit
dhcp-server
location cf2:
exit
options
dhcp-leasetime-threshold [days <days>] [hrs <hours>]
[min <minutes>] [sec <seconds>]
exit
exit
exit
When the offered lease time of the DHCP lease is less than the configured threshold, the lease is flagged to skip persistency updates and is installed with its full lease time upon a persistency recovery after a reboot.
The dhcp-leasetime-threshold command controls persistency updates for:
DHCPv4 and DHCPv6 leases for a DHCP relay or proxy (enabled with persistence subscriber-mgmt)
DHCPv4 leases for DHCP snooping in a VPLS service (enabled with persistence subscriber-mgmt)
DHCPv4 and DHCPv6 leases for a DHCP server (enabled with persistence dhcp-server)
To check if a DHCP relay or proxy lease is flagged to skip persistency updates, use the tools dump persistence submgt record record-key CLI command. When flagged to skip persistency updates, the persistency record output includes ‟Skip Persistency Updates: true”.
To check if a DHCP server lease is flagged to skip persistency updates, use the tools dump persistence dhcp-server record record-key CLI command. When flagged to skip persistency updates, the persistency record output includes ‟lease mode : LT” (LT = Lease Time) and a ‟lease time : …” field. When not flagged to skip persistency updates, the persistency record output includes ‟lease mode : ET” (ET = Expiry Time) and an ‟expires : …” field.