portfast, uplinkfast, backbonefastその2
このセクションでは、802.1d スパニングツリーのトポロジの変更プロセスとSTPタイマーへの影響を確認します。
SW3 の fa1/0 の portfast 機能を無効にしなさい。
--------
まずは、現在の設定を確認します。
SW3#show spanning-tree active | begin FastEthernet1/0
Port 41 (FastEthernet1/0) of VLAN3 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.41.
Designated root has priority 8192, address c207.153c.0000
Designated bridge has priority 32768, address c201.1621.0000
Designated port id is 128.41, designated path cost 18
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 4694, received 0
The port is in the portfast mode <--------portfast が有効になっています。
では、fa1/0 上で portfast を無効にします。
SW3#conf t
Enter configuration commands, one per line. End with CNTL/Z.
SW3(config)#interface fa1/0
SW3(config-if)#no spanning-tree portfast
確認します。
SW3#show spanning-tree interface fa1/0 portfast
VLAN3 disabled
SW3 上で、portfast を無効にしました。portfast を無効にしたので、learning, forwarding, blocking になり、スパニングツリー変更のお知らせを、ルートブリッジ
に送信するはずです。
それを確認します。
SW3 で、デバッグモードにします。そのうえで、fa1/0 をシャットダウンして、トポロジの変更を見てみます。また、fa1/0 を再度有効に(no shut)してみます。
SW3#debug spanning-tree events
Spanning Tree event debugging is on
SW3#conf t
Enter configuration commands, one per line. End with CNTL/Z.
SW3(config)#interface fa1/0
SW3(config-if)#shutdown
SW3(config-if)#
*Mar 1 03:24:37.159: STP: VLAN3 sent Topology Change Notice on Fa1/15
*Mar 1 03:24:37.159: STP: VLAN3 Fa1/0 -> blocking
SW3(config-if)#
*Mar 1 03:24:39.171: %LINK-5-CHANGED: Interface FastEthernet1/0, changed state to administratively down
*Mar 1 03:24:40.171: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0, changed state to down
SW3(config-if)#no shutdown
SW3(config-if)#
*Mar 1 03:24:46.759: STP: VLAN3 Fa1/0 -> listening
SW3(config-if)#
*Mar 1 03:24:49.735: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0, changed state to up
SW3(config-if)#
*Mar 1 03:25:01.767: STP: VLAN3 Fa1/0 -> learning
SW3(config-if)#
*Mar 1 03:25:16.779: STP: VLAN3 sent Topology Change Notice on Fa1/15
*Mar 1 03:25:16.779: STP: VLAN3 Fa1/0 -> forwarding
では、portfast を有効にして、もう一度やってみます。
SW3(config-if)#spanning-tree portfast
%Warning: portfast should only be enabled on ports connected to a single host.
Connecting hubs, concentrators, switches, bridges, etc.to this interface
when portfast is enabled, can cause temporary spanning tree loops.
Use with CAUTION
%Portfast has been configured on FastEthernet1/0 but will only
have effect when the interface is in a non-trunking mode.
SW3#show spanning-tree active | begin FastEthernet1/0
from FastEthernet1/0
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 0, notification 0, aging 300
Port 41 (FastEthernet1/0) of VLAN3 is forwarding
Port path cost 19, Port priority 128, Port Identifier 128.41.
Designated root has priority 8192, address c207.153c.0000
Designated bridge has priority 32768, address c201.1621.0000
Designated port id is 128.41, designated path cost 18
Timers: message age 0, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 129, received 0
The port is in the portfast mode
SW3(config)#interface fa1/0
SW3(config-if)#
SW3(config-if)#
SW3(config-if)#
SW3(config-if)#shutdown
SW3(config-if)#
*Mar 1 03:30:18.591: STP: VLAN3 Fa1/0 -> blocking
SW3(config-if)#
*Mar 1 03:30:20.535: %LINK-5-CHANGED: Interface FastEthernet1/0, changed state to administratively down
*Mar 1 03:30:21.535: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0, changed state to down
SW3(config-if)#no shutdown
SW3(config-if)#
*Mar 1 03:30:33.683: STP: VLAN3 Fa1/0 ->jump to forwarding from blocking
SW3(config-if)#
*Mar 1 03:30:36.639: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0, changed state to up
SW3(config-if)#end
SW3#show s
*Mar 1 03:32:04.683: %SYS-5-CONFIG_I: Configured from console by console
SW3#show spanning-tree vlan 3 brief
VLAN3
Spanning tree enabled protocol ieee
Root ID Priority 8192
Address c207.153c.0000
Cost 18
Port 56 (FastEthernet1/15)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768
Address c201.1621.0000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Designated
Name Port ID Prio Cost Sts Cost Bridge ID Port ID
-------------------- ------- ---- ----- --- ----- -------------------- -------
FastEthernet1/0 128.41 128 19 FWD 18 32768 c201.1621.0000 128.41
...
デバッグモードを元に戻します。
SW3#undebug all
お疲れさまです。次回をお楽しみに。
