Siemens S223 - Manual (Page 209)

User Manual UMN:CLI
SURPASS hiD 6615 S223/S323 R1.5
A50010-Y3-C150-2-7619 209
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.
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 BPDU RSTP BPDU
Fig. 8.20 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. 8.21 Compatibility with 802.1d (2)
8.3.3 MSTP Operation
To operate the network more effectively, the hiD 6615 S223/S323 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 rout-
ing protocol.