Illegal Vmps Client Requests - Cisco Catalyst 4500 series Administration Manual

Chapter 16 Configuring VLANs, VTP, and VMPS
If a VLAN is already assigned to this port, VMPS compares the requesting MAC address to this port:
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Illegal VMPS Client Requests

Two examples of illegal VMPS client requests are as follows:
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Overview of VMPS Clients
The following subsections describe how to configure a switch as a VMPS client and configure its ports
for dynamic VLAN membership.
The following topics are included:
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Understanding Dynamic VLAN Membership
When a port is configured as "dynamic," it receives VLAN information based on the MAC-address that
is on the port. The VLAN is not statically assigned to the port; it is dynamically acquired from the VMPS
based on the MAC-address on the port.
A dynamic port can belong to one VLAN only. When the link becomes active, the switch does not
forward traffic to or from this port until the port is assigned to a VLAN. The source MAC address from
the first packet of a new host on the dynamic port is sent to the VMPS as part of the VQP request, which
attempts to match the MAC address to a VLAN in the VMPS database. If there is a match, the VMPS
sends the VLAN number for that port. If there is no match, the VMPS either denies the request or shuts
down the port (depending on the VMPS security mode setting). See the
page 16-20
Multiple hosts (MAC addresses) can be active on a dynamic port if all are in the same VLAN. If the link
goes down on a dynamic port, the port returns to the unassigned state and does not belong to a VLAN.
Any hosts that come online through the port are checked again with the VMPS before the port is assigned
to a VLAN.
For this operation to work, the client device must be able to reach the VMPS. A VMPS client sends VQP
requests as UDP packets, trying a certain number of times before giving up. For details on how to set the
retry interval, refer to section "Configuring the Retry Interval" on page 27.
The VMPS client also periodically reconfirms the VLAN membership. For details on how to set the
reconfirm frequency, refer to section "Administering and Monitoring the VMPS" on page 27.
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If the VMPS is in secure mode, it sends a "port-shutdown" response, whether a fallback VLAN has
been configured on the server.
When a MAC-address mapping is not present in the VMPS database and "no fall back" VLAN is
configured on the VMPS.
When a port is already assigned a VLAN (and the VMPS mode is not "multiple") but a second
VMPS client request is received on the VMPS for a different MAC-address.
Understanding Dynamic VLAN Membership, page 16-23
Default VMPS Client Configuration, page 16-24
Configuring a Switch as a VMPS Client, page 16-24
Administering and Monitoring the VMPS, page 16-27
Troubleshooting Dynamic Port VLAN Membership, page 16-28
for a complete description of possible VMPS responses.
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
VLAN Membership Policy Server
"About VMPS" section on
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