Chapter 8 Configuring VLANs
How the VMPS Works
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Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
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How the VMPS Works
A switch running this software release acts as a client to the VLAN Membership
Policy Server (VMPS) and communicates with it through the VLAN Query
Protocol (VQP). When the VMPS receives a VQP request from a client switch, it
searches its database for a MAC-address-to-VLAN mapping. The server response
is based on this mapping and whether or not the server is in secure mode. Secure
mode determines whether the server shuts down the port when a VLAN is not
allowed on it or just denies the port access to the VLAN.
In response to a request, the VMPS takes one of the following actions:
•
If the assigned VLAN is restricted to a group of ports, the VMPS verifies the
requesting port against this group and responds as follows:
–
If the VLAN is allowed on the port, the VMPS sends the VLAN name to
the client in response.
–
If the VLAN is not allowed on the port, and the VMPS is not in secure
mode, the VMPS sends an access-denied response.
–
If the VLAN is not allowed on the port, and the VMPS is in secure mode,
the VMPS sends a port-shutdown response.
•
If the VLAN in the database does not match the current VLAN on the port
and active hosts exist on the port, the VMPS sends an access-denied or a
port-shutdown response, depending on the secure mode of the VMPS.
If the switch receives an access-denied response from the VMPS, it continues to
block traffic from the MAC address to or from the port. The switch continues to
monitor the packets directed to the port and sends a query to the VMPS when it
identifies a new address. If the switch receives a port-shutdown response from the
VMPS, it disables the port. The port must be manually reenabled by using the
CLI, Cluster Management software, or SNMP.
You can also use an explicit entry in the configuration table to deny access to
specific MAC addresses for security reasons. If you enter the none keyword for
the VLAN name, the VMPS sends an access-denied or port-shutdown response.