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 10.1.1.0/24
(IP Range: 10.1.1.1 to 10.1.1.255)
Guest Network
10.1.1.1 - 10.1.1.254
The CIDR 10.1.1.0/24 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
10.1.1.1 - 10.1.1.254
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
10.1.1.1 -10.1.1.62
Reserved
Range
10.1.1.64
to
10.1.1.254
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.
