70
C
HAPTER
4: V
IRTUAL
LAN
S
(VLAN
S
)
Uses of Tagged VLANs
Tagging is most commonly used to allow VLANs to span switches. The
switch-to-switch connections are typically called
trunks
. Using tags,
multiple VLANs can span multiple switches using one or more trunks. In a
port-based VLAN, each VLAN requires its own pair of trunk ports, as
shown in
Figure 9
. Using tags, multiple VLANs can span two switches
with a single trunk.
Another benefit of tagged VLANs is the ability to have a port be a
member of multiple VLANs. This is particularly useful if you have a device
(such as a server) that must belong to multiple VLANs. The device must
have a NIC that supports 802.1Q tagging.
A single port can be a member of only one port-based VLAN and only
one protocol-based VLAN. It can be a member of any number of tagged
VLANs, and all additional VLAN membership for the port must be
accompanied by tags. In addition to configuring the VLAN tag for the
port, the server must have a
Network Interface Card (NIC)
that supports
802.1Q tagging.
Assigning a VLAN Tag
When a VLAN is configured to support tagging, it is assigned a tag. As
individual ports are added to a tagged VLAN, you decide whether the
port will use a tag.
Not all ports in a tagged VLAN must be tagged. As traffic from a port is
forwarded out of the switch, the switch adds and strips tags, as required,
by the port configuration for that VLAN. The default mode of the switch
is to have all ports assigned to the VLAN named
default
with an 802.1Q
VLAN tag (VLANid) of 1 assigned.
Packets arriving tagged with a VLANid that is not configured on the
ingress port will be discarded.
Figure 10
illustrates the physical view of a network that uses tagged and
untagged traffic.
Содержание 3C17705
Страница 1: ... http www 3com com SuperStack II Switch 9100 User Guide Part No DUA1770 5AAA01 Published January 2000 ...
Страница 10: ...GLOSSARY INDEX INDEX OF COMMANDS 3COM CORPORATION LIMITED WARRANTY EMC STATEMENTS ...
Страница 14: ...14 ABOUT THIS GUIDE ...
Страница 32: ...32 CHAPTER 2 INSTALLATION AND SETUP ...
Страница 62: ...62 CHAPTER 3 ACCESSING THE SWITCH ...
Страница 80: ...80 CHAPTER 4 VIRTUAL LANS VLANS ...
Страница 86: ...86 CHAPTER 5 FORWARDING DATABASE FDB ...
Страница 98: ...98 CHAPTER 6 SPANNING TREE PROTOCOL STP ...
Страница 110: ...110 CHAPTER 7 QUALITY OF SERVICE QOS ...
Страница 124: ...124 CHAPTER 8 STATUS MONITORING AND STATISTICS ...
Страница 130: ...130 CHAPTER 9 USING THE WEB INTERFACE ...
Страница 136: ...136 CHAPTER 10 SOFTWARE UPGRADE AND BOOT OPTIONS ...
Страница 156: ...156 APPENDIX C TROUBLESHOOTING ...
Страница 162: ......
Страница 176: ...176 INDEX ...
Страница 180: ...180 INDEX OF COMMANDS ...