Network Addresses: Calculating Requirements
Intended for use with Cassatt Active Response Standard Edition V5.1.
Calculating network addresses is accomplished within the larger procedure to set up control node(s) for Cassatt Active Response:
Background and recommendations
Cassatt Active Response requires a base network from which to operate. When you install the Cassatt Active Response software, the installation program prompts you for the IP address range of this network, so you need to calculate this address range prior to installation. In general, consider
these guidelines:
|
Number of IP addresses |
Recommended for Cassatt Active Response |
254 |
Supported for Cassatt Active Response |
≤ 4094 |
Minimally, this IP range should account for the following devices:
- IP address for the Cassatt Active Response control node
- IP address for miscellaneous devices on the Cassatt network (e.g., gateways, firewalls, load balancers, etc.)
- IP address for each physical server running in the Cassatt Active Response environment
Cassatt Active Response Standard Edition integrates seamlessly into your existing application environment. It is expected that applications are operational on their own networks, so you might wonder why Cassatt Active Response also needs an IP address for those application servers. The reason is, Cassatt Active Response is capable of pooling server resources and dynamically allocating them to applications as needed. To achieve this, Cassatt Active Response internally reserves IPs for each server in its free pool. So, even though you are only using a smidgen of the automation available in Cassatt Active Response in your Standard Edition implementation, you still need to allocate enough IPs so nodes can be moved in-and-out of the free pool.
Of course, pad the range as you see fit. If you do decide to implement more advanced automation of your environment with Cassatt Active Response Premium or Data Center Editions, you can always add application-specific networks without having to modify the base Cassatt network.
Cassatt recommends that you allocate a new VLAN for the Cassatt Active Response network that is not being used by other nodes that DHCP (or to service DHCP requests). This avoids potential conflicts with an existing PXE or DHCP server.
Cassatt Active Response supports IPv6 in some contexts as noted in this document. IPv4 to IPv6 and IPv6 to IPv4 tunnels are not supported.
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Formula for calculating the base Cassatt IP address requirements
Use the following formula to calculate the number of IP addresses you need for the base Cassatt network.
(control node) +
(number of other IPs required on the
network) +
(number physical servers) +
(padding) |
Where:
(control node)
This is the static IP used for the Cassatt Active Response control node.
(number of other IPs required on the network)
Include gateway IPs, firewalls,
load balancers, sniffers, and virtual IPs (VIPs).
If you use redundant gateways, add a VIP. The
Cassatt Active Response network requires a gateway, so the minimum value
for this variable is 1.
(number physical servers)
This is the total number of physical servers you expect to run in the Cassatt Active Response
environment. Cassatt Active Response allocates IP addresses to them for the purposes of inventorying
them and placing them in the free pool even if they are already operational on their own network. (Include the number of
blade servers in a blade enclosure.)
(padding)
Padding should minimally be set to 10 for the Cassatt Active Response network. |
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Reserving static IPs and determining a contiguous range of IPs
After you've calculated the IP address pool for the main Cassatt Active Response
network, you need to divide it into:
- One or more sets of IP addresses that are reserved for devices that
require static IPs
- A range of
contiguous IP addresses that Cassatt Active Response
uses for its free pool
You must reserve static IPs and determine the contiguous range of IPs in the Cassatt Active Response network prior to installation because the installation program prompts for this information. Cassatt Active Response then uses it to
determine which IPs it can dynamically assign. If Cassatt Active Response
were to dynamically allocate an IP address that you have
otherwise statically assigned, you would end up with undesirable
system behavior. I'd recommend you separate
these now as part of your network architecture to avoid that
possible problem.
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Reserving static IPs
Cassatt Active Response requires that a few devices have static IPs:
- Control nodes and, when using dual control nodes, their VIP
- Gateways and their VIP
- BladeCenter integrated switch modules
Typically, it's common networking practice to reserve static IPs from
the start or the end of the IP range:
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Determining the contiguous IP range
After you have identified the reserved IPs you need from the start and
end of your total network space, you are left with a
range of contiguous IP addresses.
During the Cassatt Active Response installation, you need to specify
the first available IP and the last available IP in that
range, as highlighted in this diagram:
Note
that after Cassatt Active Response is up and running, you can extend this
range by reserving IPs (from anywhere in the IP range) in
the Cassatt Active Response Controller user interface.
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Network address planning sheet
We've largely worked through a big planning exercise in this article.
After you've done the work of determining various network
IP pools, static IP assignments, et al., it's
a good idea to capture that information. Click this link
for a handy little planning sheet that can be used during
the various steps of a Cassatt Active Response implementation:
Network Addresses
Planning Sheet
As your site
personnel go through the various Cassatt Active Response setup and configuration
phases, they'll thank you for
completing this planning sheet (and you'll probably
be happier with the results, too).
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CIDR prefix
Once you know how big each network needs to be, you can determine the CIDR prefix for your network size. If you really love
your binary math, you can do the calculation; otherwise, here's a cheat sheet.
You'll need the CIDR value for the Cassatt Active Response
network when you install Cassatt Active Response and for additional networks when you
add the networks to Cassatt Active Response using the Controller user interface (I'll tell you how to do that later).
The OS installation on the control node prompts for the CIDR information in netmask format for the Cassatt Active Response
network.
Once you've calculated the number of IPs you need and determined a CIDR prefix
for each network, you can get your network addresses from your admin.
Application and power networks
As I mentioned earlier, you don't have to do any calculations or make any changes to your existing application networks to use them with Cassatt Active Response Standard Edition. All you have to do is add the primary network for each tier to Cassatt Active Response so the networks are available for selection when you create your tiers.
Many sites and some hardware vendors recommend
putting power controllers on their own network for security
reasons, and it's a best practice when using Cassatt Active Response. You can assign static IPs to the power controllers manually, or use a DHCP server to assign static IP addresses. Either way, add your power control network to Cassatt Active Response so Cassatt Active Response can power your application nodes up and down.
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Adding networks to the Cassatt Active Response Controller
To add networks to Cassatt Active Response, log into the Controller and select Networks in the left navigation bar. Click the New network button. The next illustration shows the network dialog box.
Here are a couple of things you need to know:
- The network address must be in CIDR format for either IPv4 or IPv6. For an IPv6 network, you can leave the network address field blank and rely on router advertisement.
- The gateway is not a required field because networks for the private use of a single application do not need them; for most IPv4 uses, include the gateway IP. For an IPv6 network, only use a gateway IP when router advertisements are turned off for the router.
- For power only tiers (all tiers when using Standard Edition): add only the primary network and power network(s). Other application networks do not need to be managed by Cassatt Active Response.
When you click next, the reservation dialog box is displayed. Use this page to reserve IP addresses for static devices on the network.
For networks containing more than 256 addresses, reservation is only via file.
Summary
I've covered a lot of ground in this article, so I'll summarize some
of the key points about network addressing in Cassatt Active Response in
this table.
Question |
Answer |
What are the IP address requirements
for Cassatt Active Response? |
- You must have at least one network (the Cassatt Active Response
network) that is used for
creating a shared resource pool that
can be allocated in the Cassatt Active Response environment. The Cassatt Active Response network must be IPv4.
- For the Cassatt Active Response network, you need a contiguous range
of IP addresses that Cassatt Active Response can use in assigning
to resources in its free pool.
- The Cassatt Active Response network requires
static IP addresses for control nodes, gateways,
and any BladeCenter switch modules. It is good network
practice to reserve these from outside the contiguous
DHCP range. (On devices that use static IP addresses,
verify that those addresses are outside the range dynamically
allocated by Cassatt Active Response.)
- You can have as many additional networks as you need for your applications.
|
If I don't know how many IP addresses I need now, can I estimate now and add new ones later? |
I'd recommend always estimating higher rather
than lower to anticipate growth in the Cassatt Active Response network.
Remember, it needs at least one
IP for every physical server
that could run in the Cassatt Active Response environment (and potentially
one IP for every power controller). After you install
Cassatt Active Response, the only way to modify the size of the Cassatt Active Response
network is to reinstall—ouch!
|
Can Cassatt Active Response share a network? |
Yes. By default, the Cassatt Active Response installation program assumes control over the entire
network; the range of control is determined by the IP address you specify for the
first control node and the CIDR prefix you provide.
However, you can limit Cassatt Active Response control to a specific range within a network.
For the Cassatt Active Response network, you do this by entering the "First available
address on this subnet" and "Last
available address on this subnet" when you install Cassatt Active Response. The "first
available" and "last
available" define the DHCP range dedicated to Cassatt Active Response automatic assignment.
For other networks, you can use the Controller user interface to specify static
addresses that Cassatt Active Response should not dynamically allocate.
|
What is the control node virtual IP address and how is it used? |
The virtual IP address (VIP) is a common
IP address used when you have two control nodes that
always resolves to the active control node. (If you
are using only 1 control node, a VIP address is unnecessary.) |
Return to:
Installing Cassatt Active Response and Control Node Setup: Single Control Node
Installing Cassatt Active Response and Control Node Setup: Dual Control Node
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