3Com 4.2.2 manual Vlans, Protocol-based VLANs

C-12APPENDIX C: ATM AND VLAN MANAGEMENT BASICS

	Trunk (VLT). A VLT port in one switch unit must be connected only to a
	VLT port in the second switch unit so that the traffic can be switched to
	the correct VLAN.
	Tagging To distinguish between data frames belonging to different
	VLANS which are sent over a common VLT between two switch units,
	frame tagging is employed. Each frame which is sent along the VLT is
	tagged with a VLAN identifier.
	The tag is added to the frame (encapsulated) by the transmitting switch
	port and is removed by the receiving switch port, restoring the original
	frame. Alteration of the original frame only occurs in transmissions
	between switch devices and is not propagated to the rest of the network.
	Protocol-based VLANs
Protocol-based	In the LANplex 2500/6000, VLAN membership is based on a set of
vLANS	policies, or criteria, for grouping users.
	Protocol-based VLANs group one or more switch ports together for a
	specified network layer 3 protocol, such as IP or AppleTalk. These VLANs
	make flooding decisions based on the network layer protocol of the
	frame. In addition, for IP VLANs, you can also make flooding decisions
	based on layer 3 subnet address information.
	Protocol-sensitive VLANs allow the restriction of flood traffic for both
	routable and non-routable protocols. They have a relatively simple
	configuration comprising one or more protocols and groups of switch
	ports. These protocol-sensitive VLANs operate independently of each
	other and are simple to configure.
One port in multiple	Additionally, the same switch port can belong to multiple VLANs. For
VLANs	example, you could have port 1 on a LANplex assigned to several IP
	subnet VLANs, plus one IPX VLAN, one AppleTalk VLAN, and one NetBIOS
	VLAN. In a multiprotocol environment, protocol-sensitive VLANs can be
	very effective for controlling broadcast and multicast flooding.

Protocol Suite The protocol suite describes which protocol entities can comprise a protocol-based VLAN. For example, LANplex VLANs support the IP protocol suite, which is made up of the IP, ARP, and RARP protocols.