Intel 550T manual VLANs Virtual LANs

C H A P T E R 4 Advanced Configuration

VLANs (Virtual LANs)

Purpose	You can use VLANs to:
	•	Create up to 128 separate user groups
	•	Limit broadcast and multicast traffic
	•	Increase security by limiting communication between groups
	•	Allocate network resources (such as servers) to groups
	For a more comprehensive explanation of the VLAN concept, refer
	to the online help.
Warning when using STP	It is important to be aware of problems that may arise when using
	Spanning Tree and VLANs. The Spanning Tree can use alternative
	paths (such as different ports) to get messages to their destination.
	VLANs specify which ports can receive messages (see “Spanning
	Tree”, p. 54).
	Warning When using the Spanning Tree facility, use only one
		VLAN. If you use two or more VLANs, unexpected
		changes in your network topology may occur.
Policy-based VLANs	The switch or stack uses “Policy-based VLANs”. This means that the
	devices attached to the switch/stack can be grouped by any combina-
	tion of MAC address, IP address, IP net and port number; therefore,
	devices can belong to one or more VLANs.
Policy hierarchy	To avoid conflicts between two VLANs, a strict priority of the poli-
	cies is used:
	1.	MAC address
	2. IP address and IP net
	3.	Port
	Warning This means that a station learned by a MAC rule is not

learned by an IP or Port rule, and a station learned by an IP rule is not learned by a Port rule. Only stations that are not learned by MAC or IP rules are learned by a Port rule.

Note IP policies can be used only when IP learning is enabled on the respective ports.

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