Intel Express 520T User Manual page 76

C H A P T E R 4
Warning when using STP
Policy-based VLANs
Policy hierarchy
66
Advanced Configuration
Allocate network resources (such as servers) to groups
•
For a more comprehensive explanation of the VLAN concept, refer
to the online help.
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. 55).
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.
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.
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.