IBM 8275-416, User Manual

Page: 139 / 156

Untagged device to 802.1Q-compliant device (tagging only)
The primary difference in this configuration is that Station B supports tagging, but
not GVRP. As a result, VLAN membership information will not be propagated from
Station B to the switch. Therefore, the network administrator must configure Port 12
to always be included in VLAN 5. If this is not done, Station B’s frames will be
dropped as they are received at the switch because the frame’s VLAN tag does not
match the port’s VLAN membership set.
Once this configuration is complete, data flows as in the example above.
Using unique MAC addresses
All addresses in the network should be unique to ensure proper communication.
Duplicate VLAN configurations and oversubscription of switch
resources
The 8275-416 allows you the flexibility of configuring VLANs with identical port
memberships. However, duplicate VLANs can unnecessarily waste VLAN entries
and be an indication that the network design needs to be reconsidered. Too many
duplicate VLANs may also lead to an oversubscription of switch resources.
The 8275-416 always guarantees resources for all 32 ports in the Default VLAN
(VLAN 1). Up to 31 additional VLANs may be configured or registered with the
switch, with certain restrictions.
In a switch with no feature modules (that is, with only the 16 base ports which may
potentially be members of any VLAN) up to 10 ports may be included or
autodetected in
each
of the 31 available VLANs. Phrased alternatively, the switch
supports 310 individual instances of port VLAN membership distributed across
non-Default VLANs in whatever fashion you choose. You can choose a
configuration that “oversubscribes” the switch resources. However, unpredicted
results may occur. You will be notified of potential oversubscriptions by the terminal
interface message
Operation succeeded. WARNING: Resources exceeded!
A similar
message appears if you are using the Web interface to configure your switch.
Station A
Untagged
Station B
Tagged, VLAN 5
Static VLAN 5:
Ports 1, 12 fixed
Port 1:
PVID = 5
Port 12:
PVID = 1
100 /10 Mbps LINK /TxRx
EIA-232
19200 8 N 1
l
OK
Fault
1X
1 2
9X 2X 10X 3X 11X 4X 12X 5X 13X 7X 15X 6X 14X 8X 16X
Figure 79. Untagged device to 802.1Q-compliant device (tagging only) configuration
Appendix E. Introduction to Virtual LANs (VLANs)
123