3Com Switch 7750 Configuration Guide Guide

166 CHAPTER 21: PORT BASIC CONFIGURATION
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CAUTION: You are recommended to set the default VLAN ID of the local hybrid or
trunk ports to the same value as that of the hybrid or trunk ports on the peer
switch. Otherwise, packet forwarding may fail on the ports.
Adding an Ethernet Port
to Specified VLANs
You can add the specified Ethernet port to a specified VLAN. After that, the
Ethernet port can forward the packets of the specified VLAN, so that the VLAN on
this switch can intercommunicate with the same VLAN on the peer switch.
An access port can only be added to one VLAN, while hybrid and trunk ports can
be added to multiple VLANs.
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The access ports or hybrid ports must be added to an existing VLAN.
Tabl e 95 Processing of incoming/outgoing packets
Port type
Processing of an incoming packet
Processing of an outgoing
packet
If the packet
does not carry a
VLAN tag
If the packet carries a
VLAN tag
Access
Receive the packet
and add the
default tag to the
packet.
■ If the VLAN ID is just the
default VLAN ID, receive
the packet.
■ If the VLAN ID is not the
default VLAN ID, discard
the packet.
Deprive the tag from the
packet and send the packet.
Trunk ■ If the VLAN ID is just the
default VLAN ID, receive
the packet.
■ If the VLAN ID is not the
default VLAN ID but is
one of the VLAN IDs
allowed to pass through
the port, receive the
packet.
■ If the VLAN ID is neither
the default VLAN ID, nor
one of the VLAN IDs
allowed to pass through
the port, discard the
packet.
■ If the VLAN ID is just the
default VLAN ID, deprive
the tag and send the
packet.
■ If the VLAN ID is not the
default VLAN ID, keep
the original tag
unchanged and send the
packet.
Hybrid
■ If the VLAN ID is just the
default VLAN ID, deprive
the tag and send the
packet (this is the default
case).
■ If the VLAN ID is not the
default VLAN ID, deprive
the tag or keep the tag
unchanged (whichever is
done is determined by
the port hybrid vlan
vlan-id-list { tagged |
untagged } command)
and send the packet.