ADDC Solution Meaning of DHCP Address Lease Time in Virtual Link Layer Network

ADDC

In a certain node ADDC scheme, the virtual link layer network has DHCP enabled, with the lease time configured to 1 day. Some temporary virtual machines obtained addresses successfully. However, after the lease expired, new virtual machines still could not acquire addresses.

The lease configured on the virtual link layer network only affects the behavior on the virtual machine side: for example, if set to 365 days, the virtual machine will send a renewal once every 182.5 days. As long as the virtual machine normally sends renewal packets with the correct format and the DHCP controller (CTL) switch is still on, the renewal will succeed.

However, when the lease expires, the controller (CTL) will neither release the IP internally nor actively delete the corresponding vPort. The IP will only be released if the corresponding vPort is manually deleted.

In other words, if a virtual link layer network has DHCP enabled and the address pool is fully allocated, even if a virtual machine that previously obtained an address is no longer present, new virtual machines cannot come online because there are no available addresses left. Reassigning an IP to a new virtual machine solely because the lease expired could cause IP conflicts for the vPort and is not a proper implementation.

1. Manually delete unused vPorts; this will remove the IP-to-MAC mapping in the controller (CTL) and release the corresponding address.

2. Configure HostAgingTime; this is a global setting and should be cautiously configured in scenarios involving silent virtual machines.