IST at the boundary of the MSTP region and form the CST.
  • MSTP supports the following PVST extensions:
    • Content 3.3 Implementing MSTP 3.3.5 How to configure PortFast All switches are configured with the spanning tree MSTP and extend system-id syntax. However, only the distribution switches that serve as root devices have their priority changed. The steps for configuring MST are shown in Figure . Note: The MST implementation in Cisco IOS Release 12.2(25)SEC is based on the IEEE 802.1s standard. The MST implementations in earlier Cisco IOS releases are pre-standard.
    Content 3.3 Implementing MSTP 3.3.6 Configuring and Verifying MSTP Use the show spanning-tree mst command to display MSTP information. Figure shows an example of how to display MSTP configuration information, which includes the MSTP region name, revision number, and VLAN-to-MSTP instances mapping. The next example shows how to display general MSTP information. Notice that the output below is grouped by MSTP instances, starting with the IST. Switch#show spanning-tree mst
    ###### MST00 vlans mapped: 11-4094
    Bridge address 00d0.00b8.1400 priority 32768 (32768 sysid 0)
    Root address 00d0.004a.3c1c priority 32768 (32768 sysid 0)
    port Fa4/48 path cost 203100
    IST master this switch
    Operational hello time 2, forward delay 15, max age 20, max hops 20
    Configured hello time 2, forward delay 15, max age 20, max hops 20

    Interface Role Sts Cost Prio.Nbr Status
    ---------------- ---- --- --------- -------- ------------------------
    Fa4/4 Back BLK 1000 240.196 Point-to-point
    Fa4/5 Desg FWD 200000 128.197 Point-to-point
    Fa4/48 Root FWD 200000 128.240 Point-to-point Bound(STP)

    ###### MST01 vlans mapped: 1-10
    Bridge address 00d0.00b8.1400 priority 32769 (32768 sysid 1)
    Root this switch for MST01

    Interface Role Sts Cost Prio.Nbr Status

    Fa4/4 Back BLK 1000 240.196 Point-to-point
    Fa4/5 Desg FWD 200000 128.197 Point-to-point
    Fa4/48 Boun FWD 200000 128.240 Point-to-point Bound(STP) Figure demonstrates how to display spanning tree information for a specific MSTP instance - particularly, port status, costs, and forwarding roles. A switch running Rapid PVST+ or MSTP supports a built-in protocol migration mechanism that enables it to interoperate with legacy IEEE 802.1D switches. If a Rapid PVST+ or MSTP switch receives a legacy IEEE 802.1D configuration BPDU with the protocol version set to 0, it sends only IEEE 802.1D BPDUs on that port. An MST switch can also detect that a port is at the boundary of a region when it receives a legacy BPDU, an MST BPDU (version 3) associated with a different region, or an RST BPDU (version 2). However, the switch does not automatically revert to Rapid PVST+ or MSTP mode if it no longer receives IEEE 802.1D BPDUs, because it cannot determine whether the legacy switch has been removed from the link unless the legacy switch is the designated switch. Use the following command in this situation : Switch#clear spanning-tree detected-protocols This example displays MSTP information for a specific interface. Switch#show spanning-tree mst interface fastethernet 4/4

    FastEthernet4/4 of MST00 is backup blocking
    Edge port:no (default) port guard :none (default)
    Link type:point-to-point (auto) bpdu filter:disable (default)
    Boundary :internal bpdu guard :disable (default)
    Bpdus sent 2, received 368

    Instance Role Sts Cost Prio.Nbr Vlans mapped
    -------- ---- --- --------- -------- ------------------------
    0 Back BLK 1000 240.196 11-4094
    1 Back BLK 1000 240.196 1-10 This example displays MSTP information for a specific interface and a specific MSTP instance. Switch#show spanning-tree mst 1 interface fastethernet 4/4

    FastEthernet4/4 of MST01 is backup blocking
    Edge port:no (default) port guard :none (default)
    Link type:point-to-point (auto) bpdu filter:disable (default)
    Boundary :internal bpdu guard :disable (default)
    Bpdus (MRecords) sent 2, received 364

    Instance Role Sts Cost Prio.Nbr Vlans mapped
    -------- ---- --- --------- -------- -------------------------
    1 Back BLK 1000 240.196 1-10 This example displays detailed MSTP information for a specific instance. Switch#show spanning-tree mst 1 detail

    ###### MST01 vlans mapped: 1-10
    Bridge address 00d0.00b8.1400 priority 32769 (32768 sysid 1)
    Root this switch for MST01

    FastEthernet4/4 of MST01 is backup blocking
    Port info port id 240.196 priority 240 cost 1000
    Designated root address 00d0.00b8.1400 priority 32769 cost 0
    Designated bridge address 00d0.00b8.1400 priority 32769 port id 128.197
    Timers:message expires in 5 sec, forward delay 0, forward transitions 0
    Bpdus (MRecords) sent 123, received 1188

    FastEthernet4/5 of MST01 is designated forwarding
    Port info port id 128.197 priority 128 cost 200000
    Designated root address 00d0.00b8.1400 priority 32769 cost 0
    Designated bridge address 00d0.00b8.1400 priority 32769 port id 128.197
    Timers:message expires in 0 sec, forward delay 0, forward transitions 1
    Bpdus (MRecords) sent 1188, received 123

    FastEthernet4/48 of MST01 is boundary forwarding
    Port info port id 128.240 priority 128 cost 200000
    Designated root address 00d0.00b8.1400 priority 32769 cost 0
    Designated bridge address 00d0.00b8.1400 priority 32769 port id 128.240
    Timers:message expires in 0 sec, forward delay 0, forward transitions 1
    Bpdus (MRecords) sent 78, received 0
    Content 3.4 Configuring Link Aggregation with EtherChannel 3.4.1 Describing EtherChannel Companies require greater and cheaper bandwidth to run their networks, and users are becoming more impatient with any latency that occurs. The insatiable appetite for faster networks and higher availability has intensified the competition among vendors. Some years ago, Cisco came up with a method to provide substantially higher bandwidth with lower cost overhead. Cisco originally developed EtherChannel as a LAN switch-to-switch technique of inverse multiplexing of multiple Fast or Gigabit Ethernet switch ports into one logical channel. It is effectively cheaper than higher speed media while using existing switch ports. EtherChannel has developed into a cross-platform method of load balancing between servers, switches, and routers. EtherChannel can bond two, four, or eight ports (Cisco Catalyst 6500) to develop one logical connection with redundancy. The major aspects of EtherChannel are: EtherChannel does not do frame-by-frame forwarding in a round-robin fashion on each of the links. The load-balancing policy or frame distribution used is contingent upon the switch platform used. For instance, in a Cisco Catalyst 5500 switch platform, load balancing performs an X-OR calculation on the two lowest order bits of the source and destination MAC address. An X-OR operation between a given pair of addresses uses the same link for all frames. One of the primary benefits of the X-OR operation is to prevent out-of-order frames on the downstream switch. The other advantage is redundancy. If the active channel used by a connection is lost, the existing traffic can traverse over another active link on that EtherChannel. The one disadvantage of an X-OR operation is that the load on the channels might not be equal because the load-balancing policy is done on a specific header as defined by the platform or user configuration. On a Cisco Catalyst 6500 switch, load balancing can be performed on MAC addresses, IP addresses, or IP + TCP/UDP, depending on the type of Supervisor/PFC used. Use the show port capabilities command to check the module for EtherChannel feature. The default frame distribution behavior