User guide

7-2 SUMMIT SWITCH INSTALLATION AND USER GUIDE
S PANNING T REE P ROTOCOL (STP)
A port can belong to only one STPD. If a port is a member of multiple VLANs, then all
those VLANs must belong to the same STPD.
The key points to remember when conÞguring VLANs and STP are the following:
¥ Each VLAN forms an independent broadcast domain.
¥ STP blocks paths to create a loop-free environment.
¥ When STP blocks a path, no data can be transmitted or received on the blocked port.
¥ Within any given STPD, all VLANs belonging to it use the same spanning tree.
Care must be taken to ensure that STPD instances within a single Summit
Switch do not see each other in the same broadcast domain. This could happen
if, for example, another external bridge is used to connect VLANs belonging to
separate STPDs.
DEFAULTS
The default device conÞguration contains a single STPD called s0. The default VLAN is
a member of STPD s0.
All STP parameters default to the IEEE 802.1D values, as appropriate.
STP CONFIGURATIONS
When you assign VLANs to an STPD, pay careful attention to the STP conÞguration
and its effect on the forwarding of VLAN trafÞc.
Figure 7-1 illustrates a network that uses VLAN tagging for trunk connections. The
following four VLANs have been deÞned:
¥ Sales is deÞned on Switch A, Switch B, and Switch M.
¥ Personnel is deÞned on Switch A, Switch B, and Switch M.
¥ Manufacturing is deÞned on Switch Y, Switch Z, and Switch M.
¥ Engineering is deÞned on Switch Y, Switch Z, and Switch M.
¥ Marketing is deÞned on all Switches (Switch A, Switch B, Switch Y, Switch Z, and
Switch M).
SUMMIT.BK Page 2 Thursday, September 25, 1997 12:33 PM