5.2.2 Static – Manual Assignment
In many data center environments, the preferred option for servers is to permanently assign them a fixed IP address. Knowing that a server will retain its address after a reboot makes administration more straightforward. However, in some solutions, the specific address assigned to a VM carries additional significance. When this is the case, enabling the enhanced networking workflow and choosing Static – Manual (see the following figure) allows the user to manually select a specific address to be assigned to the VM being provisioned.
Figure 23. Static – Manual Address Assignment
There are a number of points to be aware of concerning manual assignment of addresses, including the following:
• The manually entered address is validated against the network subnet and an error is raised if the address is outside of the network assigned to the network.
• A manually entered address is not validated against other address assignments already present on the network, but it is tracked. The IP Allocations dialog will show which VMs have been configured with the same addresses as long as they have been configured through vCloud Director, either through the UI, or API. It should also be noted however, that vCloud Director will not power on a VM with a duplicate IP address as long as it is tracking (or aware of) both allocations of the address.
• If the address assigned comes from within a range already assigned to an IP pool on the network, the allocation is recorded, and the utilization of network address space is updated to reflect the newly assigned address.
• If the address is allocated from within the subnet configured on a network but not from an IP pool on that network, the allocation is recorded but no utilization percentage is calculated for that network.
• After there are tracked addresses in use on a network, it is not possible to assign an IP pool that contains those addresses. It is, however, possible to create multiple pools “around” and “between” them, but utilization percentages are only calculated for the IP pools, not the entire subnet.
Manual assignment of IP addresses to VMs within vCloud Director allows complete flexibility, but makes the assumption that a user (or API call) that chooses manual assignment has a good reason to do so and understands the consequences. With guest customization enabled, the VM will be configured with the entered IP address which, if incorrect, could cause service issues. Manual assignment of IP addresses is useful when for example, the VM must have its IP address set without the aid of guest customization, but the administrator wants to track the address used within vCloud Director. A static manual assignment provides that the vCloud Director database is updated even if the VM address must then be set directly through the guest OS.
