Foundation Summary 205
Table 4-27 summarizes the intermediate states of the Spanning Tree.
Table 4-28 lists the various types of tagging used by Cisco and the types of interfaces on which
they are used.
Each LAN's designated
bridge
Forwarding
The bridge forwarding the lowest-cost CBPDU
onto the segment is the designated bridge.
All other ports
Blocking
The port is not used for forwarding frames, nor
are any frames received on these interfaces
considered for forwarding.
Table 4-27
Spanning Tree Interface States
State
Forward Data
Frames?
Learn MACs Based on
Received Frames?
Transitory or
Stable State?
Blocking
No
No
Stable
Listening
No
No
Transitory
Learning
No
Yes
Transitory
Forwarding
Yes
Yes
Stable
Table 4-28
Frame Trunking/Tagging Protocols
Tagging Method
Media
Inter-Switch Link (ISL)
Fast Ethernet
802.1Q
Fast Ethernet
802.10
FDDI
LAN Emulation (LANE)
ATM
Table 4-26
Spanning Tree--Reasons for Forwarding or Blocking (Continued)
Characterization
of Port
Spanning Tree State
Explanation
ch04.fm Page 205 Monday, March 20, 2000 5:02 PM