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Configuring VLANs
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Dynamic, Static, and Excluded Port Membership
When you add ports to a protocol VLAN, IP sub-net VLAN, IPX network VLAN, or AppleTalk cable VLAN, you can
add them dynamically or statically:
• Dynamic ports
• Static ports
You also can explicitly exclude ports.
Dynamic Ports
Dynamic ports are added to a VLAN when you create the VLAN. owever, if a dynamically added port does not
receive any traffic for the VLAN’s protocol within ten minutes, the port is removed from the VLAN. However, the
port remains a candidate for port membership. Thus, if the port receives traffic for the VLAN’s protocol, the device
adds the port back to the VLAN.
After the port is added back to the VLAN, the port can remain an active member of the VLAN up to 20 minutes
without receiving traffic for the VLAN’s protocol. If the port ages out, it remains a candidate for VLAN membership
and is added back to the VLAN when the VLAN receives protocol traffic. At this point, the port can remain in the
VLAN up to 20 minutes without receiving traffic for the VLAN’s protocol, and so on.
Unless you explicitly add a port statically or exclude a port, the port is a dynamic port and thus can be an active
member of the VLAN, depending on the traffic it receives.
NOTE: You cannot configure dynamic ports in an AppleTalk cable VLAN. The ports in an AppleTalk cable VLAN
must be static. However, ports in an AppleTalk protocol VLAN can be dynamic or static.
Figure 16.7 shows an example of a VLAN with dynamic ports. Dynamic ports not only join and leave the VLAN
according to traffic, but also allow some broadcast packets of other protocol types to “leak” through the VLAN.
See “Broadcast Leaks” on page 16-10.
Figure 16.7 VLAN with dynamic protocol ports—all ports are active when you create the VLAN
Ports in a new protocol VLAN that do not receive traffic for the VLAN’s protocol age out after 10 minutes and
become candidate ports.
User-configured port-basedVLAN
Active Dynamic Ports
Active Ports
Candidate Ports
H