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IP Address Reservation in CloudStack


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  • 1. IP Address Reservation in Apache CloudStack Saksham Srivastava CloudStack Developer
  • 2. Private IP range in Guest Networks • In an Advanced zone, an IP address range or a CIDR is assigned to a network when the network is defined. • The CloudStack virtual router acts as the DHCP server and uses this CIDR for assigning IP addresses to the guest VMs. • The CIDR for a guest network is defined say (IP Range: to Guest Network - The CIDR is now used by VR as DHCP range to allocate IPs to CloudStack VMs
  • 3. The problem.. • Not able to use all 254 IPs for Guest VMs • Want to plug-in physical servers or vms not managed by CloudStack in the same network. But cannot do so !! • Wastage of IP address space Guest Network - The whole address space could be allocated to Guest VMs and cannot be used outside CloudStack
  • 4. Solution: IP Reservation Divide the large guest network into 2 address spaces 1) Guest VM CIDR: Use this only for CloudStack Guest VMs 2) Reserved Range: CloudStack will not allocate IPs to Guest VMs from this range Guest Network Use for CloudStack VMs only - Reserved Range to
  • 5. IP Reservation • Reserved Range will not be considered by CloudStack to allocate IP address to the guest VMs • Assign static IP from the Reserved Range to physical server or non-CloudStack VMs • Since the Reserved Range is a part of the network, it will still be routable from the VR.
  • 6. IP Reservation Considerations • IP Reservation is supported only in Isolated Guest networks and VPC. • IP Reservation can be applied only when the network is in Implemented state. • No IP Reservation is done by default. • Guest VM CIDR specified must be a subset of the original network CIDR. • IP Reservation is applied only if no active IPs exist outside the Guest VM CIDR in that network. • To reset an existing IP Reservation, apply IP reservation by specifying the value of network CIDR in the CIDR field.
  • 7. How to IP Reserve UI : Edit the Guest Network by specifying the Guest VM CIDR in the CIDR column API : updateNetwork: Specify the guestVmCidr listNetwork API now includes 2 new response parameters : • networkCidr : The original Cidr of the Guest network • reservedIpRange : Non CloudStack IPs
  • 8. Note • The IP Reservation is not supported if active IPs are found outside the Guest VM CIDR. • Upgrading network offering which causes a change in CIDR (such as upgrading an offering with no external devices to one with external devices) IP Reservation becomes void if any. • Using persistent networks is a good choice as there is no need to deploy VM to bring the network to implemented state.
  • 9. Resources Functional Specification: FS+-+IP+Range+Reservation+within+a+Network Documentation: