Owner's Manual

Chapter 18. STP | 543
NETGEAR 8800 User Manual
• Although a physical port can belong to multiple STPDs, any VLAN on that port can be in
only one domain. Put another way, a VLAN cannot belong to two STPDs on the same
physical port.
• Although a VLAN can span multiple domains, any LAN segment in that VLAN must be in
the same STPD. VLANs traverse STPDs only inside switches, not across links. On a
single switch, however, bridge ports for the same VLAN can be assigned to different
STPDs. This scenario is illustrated in
Figure 39.
Figure 39. VLANs Traverse Domains Inside Switches
• The VLAN partition feature is deployed under the premise that the overall inter-domain
topology for that VLAN is loop-free. Consider the case in
Figure 40, VLAN red (the only
VLAN in the figure) spans STPDs 1, 2, and 3. Inside each domain, STP produces a
loop-free topology. However, VLAN red is still looped, because the three domains form a
ring among themselves.
EX_052
S1
WrongCorrect
S2
S2
S1