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Currently in cloudstack we can add multiple public IP ranges in Advanced zone. we want to provide similar flexibility for management and guest IP ranges.
Presently we can add multiple guest IP ranges within the same subnet in Basic Zone but we cannot add IP ranges form different subnets.
This feature provides this functionality for adding guest IP ranges in Basic zone and advanced SG enabled networks.

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Validation.
#1 Will fail if the zone is not a basic zone or if forvirtual network is true.
#2 Will fail if the IP is from a different subnet, netmask and gateway should be providednew subnet is subset or superset of the existing subnet.

Implementation detail.
In cases where a IP range form a different subnet is added, we need to configure a nic ipalias on the DHCP server with a IP form the this new subnet or add this IP to the existing nic. This is required as the IP to the guest VMs is allocated using a DHCP server. So the router should have a interface on the new subnet to listen for the DHCP request coming form VMs in the new subnet.

execution flow.
#1 validate the inputs.
#2 Add the new range to the DB.
#3 When the first ip from the new subnet is allocated to the VM, create a new virtual interface ip alias to the existing nic on the VR. This virtual interface ip alias (example eth0:1) will have one of the IPs from the new subnet.

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We intend to use the deleteVlanRange API to delete the IP ranges. The operations will be atomic. this will fail if any IP form the remove range is being used. While removing we acquire a lock on the valn that is being removed. When the subnet is removed the ip alias corresponding to this subnet will be removed form the VR.
#In case if a range being removed contains the ip address on which the dhcpserver is running (ie ip alias), cloudstack will try to acquire a new ip in the same subnet. In case if there is no free ip available in the subnet the remove command will fail.

DB changes:

No Database changes are requiredcreated a new table nic_ip_aliase which is used to store the details of the ipalias created on the router per subnet.

Supported Hypervisors.

KVM, XenServer, VMware

Note:

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The implementation as of now supports only Ipv4 addresses