3Com 4500 PWR 26-Port Configuration Manual page 110

Table 6-3 Packet processing of a hybrid port
Processing of an incoming packet
For an untagged packet
If the port has already been
added to its default VLAN,
tag the packet with the
default VLAN tag and then
forward the packet.
If the port has not been
added to its default VLAN,
discard the packet.
For a tagged packet
If the VLAN ID is one of the
VLAN IDs allowed to pass
through the port, receive the
packet.
If the VLAN ID is not one of
the VLAN IDs allowed to
pass through the
discard the packet.
6-6
Processing of an outgoing
packet
Send the packet if the VLAN ID
is allowed to pass through the
port. Use the port hybrid vlan
command to configure whether
the port keeps or strips off the
tags when sending packets of a
VLAN (including the default
port,
VLAN).