HP ProCurve 9304M Installation And Configuration Manual page 340

Installation and Basic Configuration Guide
When an HP device receives a packet on a port that is a member of a VLAN, the device forwards the packet
based on the following VLAN hierarchy:
• If the port belongs to an IP sub-net VLAN, IPX network VLAN, or AppleTalk cable VLAN and the packet
belongs to the corresponding IP sub-net, IPX network, or AppleTalk cable range, the device forwards the
packet to all the ports within that VLAN.
• If the packet is a Layer 3 packet but cannot be forwarded as described above, but the port is a member of a
Layer 3 protocol VLAN for the packet's protocol, the device forwards the packet on all the Layer 3 protocol
VLAN's ports.
• If the packet cannot be forwarded based on either of the VLAN membership types listed above, but the
packet can be forwarded at Layer 2, the device forwards the packet on all the ports within the receiving port's
port-based VLAN.
Protocol VLANs differ from IP sub-net, IPX network, and AppleTalk VLANs in an important way. Protocol VLANs
accept any broadcast of the specified protocol type. An IP sub-net, IPx network, or AppleTalk VLAN accepts only
broadcasts for the specified IP sub-net, IPX network, or AppleTalk cable range.
NOTE: Protocol VLANs are different from IP sub-net, IPX network, and AppleTalk cable VLANs. A port-based
VLAN cannot contain both an IP sub-net, IPX network, or AppleTalk cable VLAN and a protocol VLAN for the
same protocol. For example, a port-based VLAN cannot contain both an IP protocol VLAN and an IP sub-net
VLAN.
Layer 2 Port-Based VLANs
On all HP devices, you can configure port-based VLANs. A port-based VLAN is a subset of ports on an HP device
that constitutes a Layer 2 broadcast domain.
By default, all the ports on an HP device are members of the default VLAN. Thus, all the ports on the device
constitute a single Layer 2 broadcast domain. You can configure multiple port-based VLANs. When you
configure a port-based VLAN, the device automatically removes the ports you add to the VLAN from the default
VLAN.
Figure 11.1 shows an example of an HP device on which a Layer 2 port-based VLAN has been configured.
Figure 11.1 HP device containing user-defined Layer 2 port-based VLAN
User-configured port-based VLAN
A port can belong to only one port-based VLAN, unless you apply 802.1q tagging to the port. 802.1q tagging
allows the port to add a four-byte tag field, which contains the VLAN ID, to each packet sent on the port. You also
can configure port-based VLANs that span multiple devices by tagging the ports within the VLAN. The tag
enables each device that receives the packet to determine the VLAN the packet belongs to. 802.1q tagging
applies only to Layer 2 VLANs, not to Layer 3 VLANs.
11 - 2
Default VLAN