Specifications

CLI Management Guide
TigerAccess™ EE
266 SMC7824M/VSW
It is same with 802.1d to block the connection of SWITCH D and SWITCH C. However,
802.1w does not need any configured time to negotiate between switches to make for-
warding state of specific port. So it is very fast progressed. During progress to forwarding
state of port, listening and learning are not needed. These negotiations use BPDU.
8.3.2.4 Compatibility with 802.1d
RSTP internally includes STP, so it has compatibility with 802.1d. Therefore, RSTP can
recognize BPDU of STP. But, STP cannot recognize BPDU of RSTP. For example, as-
sume that SWITCH A and SWITCH B are operated as RSTP and SWITCH A is connected
to SWITCH C as designated switch. Since SWITCH C, which is 802.1d ignores RSTP
BPDU, it is interpreted that switch C is not connected to any switch or segment.
Switch A
(802.1w)
Switch B
(802.1w)
Switch C
(802.1d)
STP BPDURSTP BPDU
Fig. 8.21 Compatibility with 802.1d (1)
However, SWITCH A converts a port received BPDU into RSTP of 802.1d because it can
read BPDU of SWITCH C. Then SWITCH C can read BPDU of SWITCH A and accepts
SWITCH A as designated switch.
Switch A
(802.1w)
Switch B
(802.1w)
Switch C
(802.1d)
STP BPDU
Fig. 8.22 Compatibility with 802.1d (2)
8.3.3 MSTP Operation
To operate the network more efficiently, the switch uses MSTP (Multiple Spanning-Tree
Protocol). It constitutes the network with VLAN subdividing existing LAN domain logically
and configure the route by VLAN or VLAN group instead of existing routing protocol.