Understanding Cassatt Active Response Network Manager

Intended for use with Cassatt Active Response V5.0.

The Cassatt Active Response Network Manager decouples your network configuration from your application services by introducing programmatic control over network connectivity.

Programmatic control virtualizes network resources: with Network Manager, Cassatt Active Response can allocate servers automatically to applications that have specific networking requirements—without regard to the servers' current network connections. Cassatt Active Response simply selects a server with sufficient NICs from the global resource pool and reprograms its switch port connections to meet the application's networking needs.

Default network configuration

Understanding the default network configuration for application nodes helps you understand how Network Manager changes the default configuration when allocating nodes to applications with discrete network requirements.

Single flat network

A single flat network is the baseline Cassatt Active Response configuration: you assign the subnet to Cassatt Active Response at installation time. All configurations supported by Network Manager begin with this baseline configuration, shown in the next illustration.

After installing Cassatt Active Response, you can add additional IP address ranges to your base network. You may wish to do that for the purpose of assigning specific IPs to certain applications or in order to manage blocks of IP addresses separately. In the longer term, you may add IP address ranges to increase the size of your base Cassatt Active Response network. In any of these cases, no physical segregation is involved, so think of additional IP subnets as part of the base Cassatt Active Response network.

Primary network

Each application you run in a Cassatt Active Response tier must have a "primary" network. A tier's primary network is the network Cassatt Active Response uses for booting servers, serving the tier software images, monitoring tier and server states, and other automation-related communications.

A primary network for a tier in Cassatt Active Response has two important characteristics:

• Boot NIC – When Cassatt Active Response first boots a node during server inventory, it identifies which of the node's NICs the node booted on, and records that NIC as the "boot" NIC. You can see which NIC is the boot NIC for each server by looking at the node properties page in the Cassatt Active Response Controller.
  
  Cassatt Active Response assigns the boot NIC to the primary network when it allocates a node to a tier. In a tier, the boot NIC receives the IP address listed for the node in the tier node list.
• Bonded network interface – In the primary network, Cassatt Active Response combines the boot NIC with any other NICs that are capable of being combined into a "bond" (Linux), a "team" (Windows, VMware ESX Server), or an "IP multipathing group" (Solaris). (In this article, I refer to any type of combined interface using the Linux term—"bonded"—just to avoid overcomplicating the discussion.)
  
  Bonded network interfaces provide fault tolerance for the primary network should one NIC —or the switch connected to a NIC—fail.
  
  The next illustration shows an example bonded network interface.

When only one NIC is available, Cassatt Active Response nonetheless uses a logically bonded network interface. This is to keep the network interface name consistent among servers that have different numbers of NICs.

Also, be aware that not all NICs are capable of being placed in a bond. Cassatt Active Response discovers whether the NICs are bondable during the inventory of each application node.

Cassatt Active Response ignores any NICs that are not cabled to the Cassatt Active Response network. You can configure these NICs manually to make them available to the application node software, but Cassatt Active Response does not manage them.

Network Manager–actuated network configurations

Network Manager can modify your switch configuration programmatically to support a variety of network schemes:

• Application isolation
• Applications with secondary networks via dedicated NICs
• Applications in multiple VLANs over the bonded network interface

Most Network Manager configurations require application nodes to have supported remote management controllers; for more information, see Understanding Hardware: What Works Best with Cassatt Active Response.

Application isolation

If security for an application is a concern, you can isolate the application tier in its own network with a firewall. Each time Cassatt Active Response allocates a node to the tier, Cassatt Active Response reconfigures the switch ports for the tier's VLAN. The tier's VLAN becomes the primary network for allocated nodes, which no longer connect directly to the Cassatt Active Response network, as shown in the next illustration.

Cassatt Active Response bonds the NICs in the same way for a primary network that's isolated in a VLAN as it does when the primary network is the Cassatt Active Response network.

Applications with secondary networks via dedicated NICs

For applications that require them, you can configure one or more secondary networks. Oracle 10g RAC, for example, requires a secondary network that uses a dedicated interface to serve as a private interconnect for internode communication.

You can limit a secondary network to a single tier when your application requires a private interconnect—like Oracle 10g RAC—or you can assign a secondary network to multiple tiers that require inter-application communications that must be isolated from the Cassatt Active Response base network.

When the network is intentionally set up for private use, no gateway is used for the network as communications should not be routable to the control node (and consequently application nodes cannot boot via a NIC dedicated for secondary network use).

You can configure a tier with multiple secondary networks using additional dedicated NICs.

To allocate an application node to a tier with dedicated networks, Cassatt Active Response omits a NIC from the primary network/bond for each secondary network as shown in the next diagram. To be allocated to a tier with dedicated networks, each node must have sufficient NICs to provide:

• At least one NIC for the primary network
• One NIC for each dedicated network

Be aware that using a dedicated NIC for a network compromises resilience to NIC failure.

Applications in multiple VLANs over the bonded interface

The third Network Manager option is to use VLAN interfaces with the bonded interfaces to reliably connect an application tier to several networks. This option provides logical connectivity without dedicated hardware.

For this configuration, Cassatt Active Response aggregates all VLANs assigned to the tier into the bonded network interface.

Multiple VLANs is not supported for Windows with Cassatt Active Response, and is supported with limited hardware for Solaris.

Combining Network Manager options

If your application requires it, you can use more than one Network Manager option for a given tier. For example, your application might need both network isolation and a network with a dedicated NIC, as shown in the next illustration.

Setting up Network Manager–actuated options: high level view

1. In addition to the original Cassatt Active Response base network, which you define at Cassatt Active Response installation, you can add networks to Cassatt Active Response at any time. For each network, you specify the subnet information, the VLAN number, and the default gateway (when needed).
2. For each switch, Cassatt Active Response lets you decide whether to have Cassatt Active Response control the configuration. This option keeps your current networking setup intact without Cassatt Active Response interference for things that you want to control outside Cassatt Active Response, like a dedicated backup network. Once you designate a switch for Cassatt Active Response to configure, Cassatt Active Response discovers each application node's NIC connections to switch ports during node inventory.
3. When you create a tier to run an application, you assign the appropriate networks, specifying those that must use a dedicated NIC for the tier. Cassatt Active Response configures the image instances for the tier with the interface information for each network assigned to the tier, including IP addresses.
4. When Cassatt Active Response allocates application nodes to the tiers, it selects only nodes with enough NICs connected to Cassatt Active Response–controlled switches to meet all of the network requirements (both bonded and dedicated).
5. For each application node that is allocated to a tier, Cassatt Active Response reprograms the switch to configure the node's ports into the proper VLANs.
6. When you activate the tier, Cassatt Active Response boots the allocated servers, establishing the interface connections in each of the specified networks based on the interface information and IP addresses in the tier's image instances.

Next steps

• For information on calculating network addresses see Network Addresses: Calculating Requirements.
• For information on how to add networks and switches to Cassatt Active Response, see the online help in the Cassatt Active Response Controller.
• For details on setting up networking for your application, refer to blueprints.

Summary

The Cassatt Active Response product provides solutions to a challenging and complex IT environment. With the introduction of Network Manager, Cassatt Active Response provides many useful networking features that meet the needs of most business applications. The following table gives a quick summary of Network Manager features with supported hardware and operating systems.

	Tier isolation	Secondary networks via dedicated NICs	Multiple VLANs via aggregation
IA32/Linux
VMware ESX 3.0 VM/Linux
Xen VM/Linux
VMware ESX 3.0 VM/Windows
Sparc/Solaris			*

*Some Sparc hardware does not support VLAN interfaces.

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