HP StorageWorks XPath OS 7.4.X Administrator Guide (AA-RVHDD-TE, February 2006)

92 Using ISL trunking

data-frame-by-data-frame level, load is instead rebalanced each time an initiator or target device's

connection or disconnection impacts the routing behavior of a given ISL path.

All ingress ports share all available routes to a destination domain. There is a maximum of 16 routes to a

destination domain.

In the fabric illustrated in Figure 19, Domain 100 egress ports 1, 2, 3, and 4 can be used to reach

destination Domain 200. All these egress ports have an equal cost of 1000 (routes through Domain 100

ports 1, 2, and 3 are direct 1-Gbit/sec links to Domain 200; the route through Domain 100, Port 4 to

Domain 300 and then to Domain 200 has two 2-Gbit/sec links). The host port (Domain 100, port 6) has

all these egress ports available for routing frames to Domain 200, Port 11.

Figure 19 Sample exchange-based trunking configuration

The following are characteristics of exchange-based trunking:

• Any E_Port can be part of the trunk (and can be connected to any port).

• No interaction between the switches is required to enable the feature.

• Any mixture of link speed E_Ports is supported; all links must have an equal cost to the destination

domain.

• Load balancing distribution might not be exactly equal; in a four-port trunk, for example, the load

sharing might not be exactly 25% each.

• Load balancing is ineffective if the exchange ID does not vary (for example, same OX_ID usage).

However, this is not a problem with typical FC-4 protocols like FCP, IP over Fibre Channel, and so on.

Enabling trunking

Exchange-based trunking is activated when the appropriate license bundle is installed. You can activate it

by entering a license key, available from your switch supplier, and using the trunkSet command. When

exchange-based trunking is activated, trunking is automatically implemented for any eligible ISLs. Trunking

is enabled or disabled separately on each switch. You are not required to have exchange-based trunking

enabled or disabled uniformly across a fabric or on multiple FCRs.

You can verify and activate licenses through the command line interface (CLI) or through Advanced Web

Tools. For instructions on activating a license, see “”Licensed features” on page 24” or the HP

StorageWorks XPath OS 7.4.x Advanced Web Tools administrator guide.

ISL trunking is supported in HP fabrics, but not in McDATA or mixed fabrics.

Managing trunking

This section provides information on managing exchange-based trunking on a switch.

NOTE: The trunking feature is disabled by default and can be enabled only after the trunking license is

installed.

Host

Domain=100 Domain=200

Target

Domain=300

1 Gbit/sec (link cost 1000)

Exchange-Based Trunk

2 Gbit/sec (link cost 500)