© Copyright IBM Corp. 2011 Chapter 8. VLANs 97
As shown in Figure 4, the untagged packet is marked (tagged) as it leaves the
switch through port 5, which is configured as a tagged member of VLAN 2. The
untagged packet remains unchanged as it leaves the switch through port 7, which is
configured as an untagged member of VLAN 2.
Figure 4. 802.1Q tagging (after port-based VLAN assignment)
In Figure 5, tagged incoming packets are assigned directly to VLAN 2 because of
the tag assignment in the packet. Port 5 is configured as a tagged member of VLAN
2, and port 7 is configured as an untagged member of VLAN 2.
Figure 5. 802.1Q tag assignment
As shown in Figure 6, the tagged packet remains unchanged as it leaves the switch
through port 5, which is configured as a tagged member of VLAN 2. However, the
tagged packet is stripped (untagged) as it leaves the switch through port 7, which is
configured as an untagged member of VLAN 2.
BS45012A
Port 6 Port 7 Port 8
Port 1
Port 4
Port 5
Port 2 Port 3
802.1Q Switch
Key
Priority
CFI
VID
- User_priority
- Canonical format indicator
- VLAN identifier
PVID = 2
Tagged member
of VLAN 2
Untagged memeber
of VLAN 2
After
DA
SA
Data
CRC
(*Recalculated)
Outgoing
untagged packet
(unchanged)
DASADataCRC* Ta g
VID = 2Priority
16 bits 3 bits 1 bits 12 bits
8100 CFI
Port 6
DASATagDataCRC
Tagged packet
BS45013A
Port 7 Port 8
Port 1
Port 4
Port 5
Port 2 Port 3
802.1Q Switch
PVID = 2
Untagged member
of VLAN 2
Tagged member
of VLAN 2
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