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IP Address Zones in Subnets

An IP address zone is a group of host IP addresses and array data IP addresses in a subnet. When using two switches for iSCSI traffic, hosts can achieve better performance by establishing iSCSI connections with data IP addresses inside the same zone, as opposed to establishing iSCSI connections with data IP addresses in a different zone.

Note: IP address zones are not required for Fibre Channel arrays.

The IP addresses within a subnet can be divided into the following IP address zone types:

IP Address Zones Types
Zone Type Description
None Used for non-iSCSI enabled subnets.
Single All IP addresses are in one zone. This is the default zoning setting.

With two network switches, iSCSI connections can be routed over the inter-switch link.
Bisect One zone includes the IP addresses from the top half of the subnet; for example, 192.168.1.128 to 192.168.1.254. The other zone takes the IP addresses from the bottom half of the subnet; for example, 192.168.1.1 to 192.168.1.127
Even/Odd The IP addresses are grouped by their last bit. One zone includes the even-numbered IP addresses, such as 192.168.1.2, 192.168.1.4, 192.168.1.6, and so on. The other zone includes the odd-numbered IP addresses, such as 192.168.1.1, 192.168.1.3, 192.168.1.5, and so on.

IP address zones are useful for configurations that use two switches, where you want to establish connections that avoid the Inter-Switch Link. For IP address zones to work, the host and the array must have its data IP addresses configured with half of its IP addresses from one zone connected to one switch and the other half of its IP addresses from the other zone connected to the other switch. For example, assume that:

  • There is single subnet, 192.168.1.0/24.
  • There are two zones, defined as Red and Blue.
  • Red zone consists of:
    • Host IP 192.168.1.1
    • Array Data IP 192.168.1.3
    • Array Data IP 192.168.1.5
  • Blue zone consists of:
    • Host IP 192.168.1.2
    • Array Data IP 192.168.1.4
    • Array Data IP 192.168.1.6

In the IP Address Zone, the host IP addresses in the Red zone only establish connections with the data IP addresses in the Red zone. And the host IP addresses in the Blue zone only establish connections with the data IP addresses in the Blue zone. In this way, iSCSI connections do not use inter-switch link and thereby maximize I/O performance.

IP Address Zones
  1. Host
  2. Switch 1
  3. Switch 2
  4. Array
  5. Inter-switch link
Parent topic: Subnets