150 C HAPTER 8: TRUNKINGDefining Trunks To define a trunk, you specify the ports that you want to be in the trunk.ImportantConsiderationsn If you have already defined other trunks on your system, you cannotselect ports that are part of an existing trunk.n Devices that you use in a trunking configuration must have thehardware to support the trunking algorithm.n You can define more than one trunk at a time, which saves having toreboot the system after each trunk definition.n When you define a trunk, you specify ports and characteristicsassociated with the trunk (including Gigabit Ethernet flow control).You can specify them all in one define operation.n When you create the trunk, the entire trunk assumes the current portcharacteristics, such as the FDDI station mode [dual attach station(DAS) or single attach station (SAS)].n Trunk names can be no longer than 32 characters.n 3Com recommends that the TCMP state be enabled. But devices canoperate without TCMP. When TCMP is not in effect on apoint-to-point link, its configuration validation is simply absent.n If your system has more than one media type (for example, FDDI, FastEthernet, and Gigabit Ethernet), you are prompted for a media typebefore you are prompted for the trunk information.n Trunk names become the port labels when you display information onthe trunks.n All ports in the trunk are set to the selected operating mode(half-duplex or full-duplex).n Each Gigabit Ethernet module that you install takes up one of theswitch’s four trunk resources (but does not itself constitute a trunk). Ifyou have two or more Gigabit Ethernet modules, you can trunk themtogether to free up switch trunk resources. For example, if you installthree Gigabit Ethernet modules, the switch allows only one additionaltrunk. But if you trunk the Gigabit Ethernet modules, the switchsupports three additional trunks after you reboot.If you add a Gigabit Ethernet module to a switch that has four trunksalready defined, the module does not power up, and you receive anerror message.
