PVST+

Test : PVST+ im gemischten Cisco / Extreme - Umfeld

Ausgangslage / Anforderung :
Für ein Campusweites L2-Netzwerk werden L2-Switche der Hersteller Cisco und Extreme-Network eingesetzt. In der oben angezeigten Ring-Struktur soll das Per-Vlan Spanningtree Protokoll (PVST+) eingesetzt werden. Da mehrere VLANs vorhanden sind, sollen die Root-Bridges auf die verschiedenen Switche verteilt werden

Erwartetes Ergebnis :
Es soll eine möglichst störungsfreie STP-Umgebung betrieben werden. Auch bei Ausfall einzelner Komponenten soll das STP einen Broadcaststurm (L2-Loop) verhindern. Die Rootbridge soll dann auf dem jeweils im Uhrzeigersinn folgenden Switch etabliert werden.

Konfigurationen :
Auf allen vier Switchen wurden die Vlans angelegt (bei Cisco wurde der VTP- Modus auf transparent geschaltet). Die Switche sind full-meshed (via Trunks) miteinander verbunden, so daß definitv ein STP- Algorithmus für den fehlerfreien Betrieb installiert sein muß. Jeder Switch ist die Rootbridge für jeweils ein Vlan (Switch1 = Vlan_A (Vlan11) ; Switch2 = Vlan_B (Vlan12) ; Switch3 = Vlan_C (Vlan13) ; Switch4 = Vlan_D (Vlan14)).
Für den Fall des Falles wurden händisch bereits die “Ersatz-Rootbridges” festgelegt, so daß zum Beispiel Switch 2 Rootbridge für VLan_A wird, sollte Switch 1 ausfallen.

Konfig Switch 1 (Extreme Summit 48si)
Konfig Switch 2 (Extreme Summit 48si)
Konfig Switch 3 (Cisco Catalyst 3750)
Konfig Switch 4 (Cisco Catalyst 3750)

Testdurchlauf :
Zunächst wurde der Switch 2 (Extreme Summit 48si) einfach mal ausgeschaltet. Von der der Idee her sollte der Switch3 (Cisco 3750) nun Rootbridge für Vlan12 (Vlan_B) werden und zugleich Rootbridge für Vlan13 (Vlan_C) bleiben. Wie beim Vergleich der Mac-Adressen zu sehen ist, klappt dies hier auch wunderbar.

Vor dem Ausschalten von Switch2 :

SWITCH_3#sh span vlan 12

VLAN0012
Spanning tree enabled protocol ieee
Root ID Priority 0
   Address 0004.9615.fee0
   Cost 19
   Port 13 (GigabitEthernet1/0/13)
   Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 4108 (priority 4096 sys-id-ext 12)
   Address 0012.7fb5.6e00
   Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
   Aging Time 300

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi1/0/1 Desg FWD 19 128.1 P2p
Gi1/0/13 Root FWD 19 128.13 P2p
Gi1/0/24 Desg FWD 4 128.24 P2p

SWITCH_3#

Switch2 wird ausgeschaltet :

SWITCH_3#
SWITCH_3#sh deb
Spanning Tree:
Spanning Tree event debugging is on
SWITCH_3#
SWITCH_3#
SWITCH_3#
SWITCH_3#
2d23h: STP: VLAN0001 sent Topology Change Notice on Gi1/0/24
2d23h: STP: VLAN0012 we are the spanning tree root
2d23h: STP: VLAN0014 sent Topology Change Notice on Gi1/0/24
2d23h: STP: VLAN0013 Topology Change rcvd on Gi1/0/24
2d23h: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/13, ch
anged state to down
2d23h: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/13, changed state to down
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 heard root 12288-0004.9603.8990 on Gi1/0/1
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 heard root 8204-0012.7fb4.f300 on Gi1/0/24
2d23h: STP: VLAN0012 heard root 8204-0012.7fb4.f300 on Gi1/0/1
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/1
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0012 Topology Change rcvd on Gi1/0/1
SWITCH_3#
SWITCH_3#
SWITCH_3#sh span vlan 12

VLAN0012
Spanning tree enabled protocol ieee
Root ID Priority 4108
   Address 0012.7fb5.6e00
   This bridge is the root
   Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 4108 (priority 4096 sys-id-ext 12)
   Address 0012.7fb5.6e00
   Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
   Aging Time 300

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi1/0/1 Desg FWD 19 128.1 P2p
Gi1/0/24 Desg FWD 4 128.24 P2p

SWITCH_3#
SWITCH_3#
SWITCH_3#sh span vlan 13

VLAN0013
Spanning tree enabled protocol ieee
Root ID Priority 13
   Address 0012.7fb5.6e00
   This bridge is the root
   Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 13 (priority 0 sys-id-ext 13)
   Address 0012.7fb5.6e00
   Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
   Aging Time 300

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi1/0/1 Desg FWD 19 128.1 P2p
Gi1/0/24 Desg FWD 4 128.24 P2p

SWITCH_3#

Auch beim Wiedereinschalten des Switch2 klappt alles wie erwartet. Die Rootbridge für Vlan12 ist nun wieder Switch 2 :

Switch 2 wieder an :

SWITCH_3#
SWITCH_3#
SWITCH_3#
2d23h: STP: VLAN0012 heard root 0-0004.9615.fee0 on Gi1/0/1
2d23h: supersedes 4108-0012.7fb5.6e00
2d23h: STP: VLAN0012 new root is 0, 0004.9615.fee0 on port Gi1/0/1, cost 38
2d23h: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/13, changed state to up
2d23h: set portid: VLAN0001 Gi1/0/13: new port id 800D
2d23h: STP: VLAN0001 Gi1/0/13 -> listening
2d23h: set portid: VLAN0010 Gi1/0/13: new port id 800D
2d23h: STP: VLAN0010 Gi1/0/13 -> listening
2d23h: set portid: VLAN0011 Gi1/0/13: new port id 800D
2d23h: STP: VLAN0011 Gi1/0/13 -> listening
2d23h: set portid: VLAN0012 Gi1/0/13: new port id 800D
2d23h: STP: VLAN0012 Gi1/0/13 -> listening
2d23h: set portid: VLAN0013 Gi1/0/13: new port id 800D
2d23h: STP: VLAN0013 Gi1/0/13 -> listening
2d23h: set portid: VLAN0014 Gi1/0/13: new port id 800D
2d23h: STP: VLAN0014 Gi1/0/13 -> listening
2d23h: STP: VLAN0012 new root port Gi1/0/13, cost 19
2d23h: STP: VLAN0011 Gi1/0/13 -> blocking
2d23h: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/13, ch
anged state to up
SWITCH_3#
SWITCH_3#
SWITCH_3#
2d23h: STP: VLAN0001 Gi1/0/13 -> learning
2d23h: STP: VLAN0010 Gi1/0/13 -> learning
2d23h: STP: VLAN0012 Gi1/0/13 -> learning
2d23h: STP: VLAN0013 Gi1/0/13 -> learning
2d23h: STP: VLAN0014 Gi1/0/13 -> learning
2d23h: STP: VLAN0013 Topology Change rcvd on Gi1/0/1
2d23h: STP: VLAN0013 Topology Change rcvd on Gi1/0/24
2d23h: STP: VLAN0001 sent Topology Change Notice on Gi1/0/24
2d23h: STP: VLAN0001 Gi1/0/13 -> forwarding
2d23h: STP: VLAN0010 Gi1/0/13 -> forwarding
2d23h: STP: VLAN0012 sent Topology Change Notice on Gi1/0/13
2d23h: STP: VLAN0012 Gi1/0/13 -> forwarding
2d23h: STP: VLAN0013 Gi1/0/13 -> forwarding
2d23h: STP: VLAN0014 sent Topology Change Notice on Gi1/0/24
2d23h: STP: VLAN0014 Gi1/0/13 -> forwarding
SWITCH_3#
SWITCH_3#
SWITCH_3#sh span vlan 12

VLAN0012
Spanning tree enabled protocol ieee
Root ID Priority 0
   Address 0004.9615.fee0
   Cost 19
   Port 13 (GigabitEthernet1/0/13)
   Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 4108 (priority 4096 sys-id-ext 12)
   Address 0012.7fb5.6e00
   Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
   Aging Time 300

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi1/0/1 Desg FWD 19 128.1 P2p
Gi1/0/13 Root FWD 19 128.13 P2p
Gi1/0/24 Desg FWD 4 128.24 P2p

SWITCH_3#

Jetzt bleibt noch zu belegen, daß auch ein Extreme-Switch die Rootbridge vom Cisco-Switch übernehmen kann. Dazu wird nun Switch4 ausgeschaltet, auf das Switch1 übernimmt :

Switch4 ist eingeschaltet :
#
* Summit48si:99 #
* Summit48si:99 # sh stpd s14
Stpd: s14 Stp: ENABLED Number of Ports: 3
Rapid Root Failover: Disabled
802.1Q Tag: 14
Ports: 1,17,48
Active Vlans: vlan14
Bridge Priority: 4096
BridgeID: 10:00:00:04:96:03:89:90
Designated root: 00:0e:00:12:7f:b4:f3:00
RootPathCost: 19 Root Port: 17
MaxAge: 20s HelloTime: 2s ForwardDelay: 15s
CfgBrMaxAge: 20s CfgBrHelloTime: 2s CfgBrForwardDelay: 15s
Topology Change Time: 35s Hold time: 1s
Topology Change Detected: FALSE Topology Change: FALSE
Number of Topology Changes: 9
Time Since Last Topology Change: 188s
* Summit48si:100 #
#
Switch4 ist ausgeschaltet :
#
* Summit48si:100 # sh stpd s14
Stpd: s14 Stp: ENABLED Number of Ports: 3
Rapid Root Failover: Disabled
802.1Q Tag: 14
Ports: 1,17,48
Active Vlans: vlan14
Bridge Priority: 4096
BridgeID: 10:00:00:04:96:03:89:90
Designated root: 10:00:00:04:96:03:89:90
RootPathCost: 0 Root Port: ----
MaxAge: 20s HelloTime: 2s ForwardDelay: 15s
CfgBrMaxAge: 20s CfgBrHelloTime: 2s CfgBrForwardDelay: 15s
Topology Change Time: 35s Hold time: 1s
Topology Change Detected: TRUE Topology Change: TRUE
Number of Topology Changes: 10
Time Since Last Topology Change: 0s
#
#
Switch4 wieder eingeschaltet :
#
* Summit48si:101 # sh stpd s14
Stpd: s14 Stp: ENABLED Number of Ports: 3
Rapid Root Failover: Disabled
802.1Q Tag: 14
Ports: 1,17,48
Active Vlans: vlan14
Bridge Priority: 4096
BridgeID: 10:00:00:04:96:03:89:90
Designated root: 00:0e:00:12:7f:b4:f3:00
RootPathCost: 19 Root Port: 17
MaxAge: 20s HelloTime: 2s ForwardDelay: 15s
CfgBrMaxAge: 20s CfgBrHelloTime: 2s CfgBrForwardDelay: 15s
Topology Change Time: 35s Hold time: 1s
Topology Change Detected: FALSE Topology Change: TRUE
Number of Topology Changes: 11
Time Since Last Topology Change: 225s

* Summit48si:102 #

Erhaltenes Ergebnis :
Das PVST (Per Vlan Spanning Tree) funktioniert in einer gemischten Cisco / Extreme - Umgebung einwandfrei.


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