Introduction:
This document describes how to connect SG300 with Catalyst switch via STP.
Spanning Tree Protocol (STP) is a Layer 2 protocol that runs on mainly on switches. The specification for STP is IEEE 802.1D. The main purpose of STP is to ensure that you do not create loops when you have redundant paths in your layer 2 network.
STP stands for spanning tree protocol, RSTP stands for rapid STP, MSTP stands for multiple STP.
Catalyst switch default STP mode is PVST+, which runs STP for each VLAN, and encapsulates STP BPDU with VLAN tag (except VLAN 1).
For example, PVST+ BPDU for VLAN 2 is tagged with VLAN 2. While PVST+ BPDU for VLAN 1 is untagged.
Catalyst also supports rapid-PVST+ mode, which runs RSTP for each VLAN. STP BPDU is also encapsulated with VLAN tag.
PVST+ can setup different topology for different VLAN to achieve VLAN load balance.
SMB switch default STP mode is RSTP, and supports MSTP. SMB does not support PVST+ or rapid-PVST+.
Note: By default, Catalyst trunk allows all VLANs, while SMB switch allows no VLAN.
We need to remove extra VLANs from Catalyst and add required VLANs in SMB trunk to make VLANs match.
SMB switch can use default RSTP to connect to Catalyst switch in default PVST+ or rapid-PVST+ mode:
In this case, SMB switch and Catalyst switch are in different mode, there is boundary between them.
SMB STP communicates with Catalyst STP instance for VLAN 1. Catalyst STP BPDU for other VLANs pass through SMB switch as normal traffic.
If Catalyst in PVST+ mode is root for VLAN 1, then PVST+ load balance cannot be achieved since SMB switch blocks all VLAN tagged PVST+ BPDU.
But if we setup SMB switch as root, load balance can be achieved:
This is due to SMB switch ports are in forwading state and Catalyst tagged PVST+ BPDUs are passed through SMB STP region.
While in the diagram above, we need to use port priority to balance VLAN load, which is not a very trivial design.
So recommended connection mode is MSTP between SMB and Catalyst switch.
MSTP has multiple Spanning tree instances to build different topology for different vlan groups mapped to instance.
That can be used for VLAN load balance, as illustrated below:
vlan 1-10 are mapped to MSTP instance 1
vlan 11-20 are mapped to MSTP instance 2
D1 is root for vlan 1-10, D2 is root for vlan 11-20.
SG300/500 as access switch dual-homed to two distribution layer catalyst switches.
SG300/500 load balance vlan 1-10 to uplink to D1 and vlan 11-20 to uplink to D2.
Note:
In order for MSTP to work properly, please configure the name, revision number, and vlan to instance mapping to be the sam
across connected MSTP switches. These switches are said to be in the same MSTP region.
Connectivity for switches in different MSTP regions is beyond the scope of this document.
For more information regarding Catalyst MSTP, please refer to
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfc.shtml
Topology Diagram:
SG300 and 2 Catalyst form a triangle:
(f0/2) SW1.3560 (f0/4)-----(Gi1)SG300 (Gi8) --------(G0/2) SW2.3560 (g0/1)
Configuration Overview:
SG300#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - VoIP Phone
M - Remotely-Managed Device, C - CAST Phone Port,
W - Two-Port MAC Relay
Device ID Local Adv Time To Capability Platform Port ID
Interface Ver. Live
------------------ ----------- ---- ------- ---------- ------------ -----------
SW1 gi1 2 120 R S I cisco FastEtherne
WS-C3560-8PC t0/4
SW2 gi8 2 138 R S I cisco GigabitEthe
WS-C3560C-8P rnet0/2
C-S
SG300(config)#do sh mac add
Aging time is 300 sec
Vlan Mac Address Port Type
-------- --------------------- ---------- ----------
1 00:1a:e3:73:50:05 gi1 dynamic
1 18:33:9d:03:a7:c0 gi1 dynamic
1 64:d8:14:5d:14:13 0 self
SG300(config)#do sh arp
Total number of entries: 2
VLAN Interface IP address HW address status
--------------------- --------------- ------------------- ---------------
vlan 1 1.1.1.1 00:1a:e3:73:50:40 dynamic
vlan 1 gi1 1.1.1.2 18:33:9d:03:a7:c0 dynamic
[
SW1 MAC: 00:1a:e3:73:50:40
SW2 MAC: 18:33:9d:03:a7:c0
SG300 MAC: 64:d8:14:5d:14:13
]
[SG300/3560 Spanning Tree Configuration]
SG300 does not support PVST (per vlan spanning tree) or rapid-PVST, uses MSTP to connect to Catalyst 3560 switch.
SG300 configration is the same as Catalyst switch.
spanning-tree mode mst
spanning-tree mst configuration
name TEST
Since SW1 has lowest MAC, it will be elected as ROOT.
SW2 has lower MAC than SG300, and is elected as designated for link with SG300.
SG300 Gi8 port will be blocked.
SG300#sh spanning-tree mst-configuration [25 seconds]
Gathering information ..........
Current MST configuration
Name: TEST
Revision: 0
Instance Vlans Mapped State
-------- ------------------------------------------------ -----
0 1-4094 enabled
SG300#sh spanning-tree active [15 seconds]
Spanning tree enabled mode MSTP
Default port cost method: long
Gathering information ..........
###### MST 0 Vlans Mapped: 1-20
CST Root ID Priority 32768
Address 00:1a:e3:73:50:00
The IST ROOT is the CST ROOT
Root Port gi1
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
IST Master ID Priority 32768
Address 00:1a:e3:73:50:00
Path Cost 200000
Rem hops 19
Bridge ID Priority 32768
Address 64:d8:14:5d:14:13
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Max hops 20
Name State Prio.Nbr Cost Sts Role PortFast Type
--------- -------- --------- -------- ------ ---- -------- -----------------
gi1 enabled 128.49 200000 Frw Root No P2P Intr
gi8 enabled 128.56 20000 Blk Altn No P2P Intr
----------------------------------------------------------------------------------------------------------------------------------------
SW1(config)#do sh span
MST0
Spanning tree enabled protocol mstp
Root ID Priority 32768
Address 001a.e373.5000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
Address 001a.e373.5000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 200000 128.3 P2p
Fa0/4 Desg FWD 200000 128.5 P2p
SW2#sh span
MST0
Spanning tree enabled protocol mstp
Root ID Priority 32768
Address 001a.e373.5000
Cost 0
Port 1 (FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
Address 1833.9d03.a780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 200000 128.1 P2p
Gi0/2 Desg FWD 20000 128.10 P2p
Now let's change SG300's priority to 0 to make it ROOT
SG300(config)#spanning-tree priority 0
We can see now SG300 is root
SW1#sh span
MST0
Spanning tree enabled protocol mstp
Root ID Priority 0
Address 64d8.145d.1413
Cost 0
Port 5 (FastEthernet0/4)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
Address 001a.e373.5000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/2 Altn BLK 200000 128.3 P2p
Fa0/4 Root FWD 200000 128.5 P2p
And SW2 elected as designated switch due to its link cost to ROOT switch is better [1000M] than SW1 [100M]
We can modify interface level spanning tree parameters:
SG300(config)#int gi 1
SG300(config-if)#spanning-tree
bpdu Configure BPDU handling when STP is disabled.
bpduguard Protect network from unexpected BPDU packets
cost Change an interface's spanning tree path cost
disable Disable spanning-tree on an interface
guard Guard the interface
link-type Override the default link-type setting
mst Configure the MSTP Subsystem
port-priority Change an interface's spanning tree priority (in steps
of 16)
portfast Allow to move directly to the forwarding state when
linkup occurs
[bpdu filter]
SG300(config-if)#spanning-tree bpdu
filtering Specify that when spanning tree is disabled on the
interface, BPDU packets would be filtered.
flooding Specify that when spanning tree is disabled on the
interface, untagged BPDU packets would be flooded
unconditionally (Without applying VLAN rules), to all
ports with spanning tree disabled. Tagged BPDU packets
would be filtered.
[root guard]
SG300(config-if)#spanning-tree guard
root Guard the interface from becoming root port
SG300(config-if)#spanning-tree mst 1
cost Change an interface Spanning Tree path cost for a
specific instance.
port-priority Change an interface Spanning Tree priority (in steps
of 16) to a specific instance.
SG300(config-if)#spanning-tree link-type
point-to-point Specify that the link type of a port is point-to-point
shared Specify that the link type of a port is shared
And we can also tune spanning tree parameters:
SG300(config)#spanning-tree
bpdu Configure BPDU handling when STP is disabled.
forward-time Set a Spanning Tree FORWARD Interval
hello-time Set a Spanning Tree HELLO Interval
max-age Set a Spanning Tree MAX AGE Interval
mode Spanning tree protocol type
mst Configure MSTP Subsystem
pathcost Spanning tree path-cost method
priority Specify a Spanning Tree Priority (in steps of 4096)
<CR>
SG300(config)#spanning-tree hello-time
<1-10> Set a Spanning Tree HELLO Interval
SG300(config)#spanning-tree hello-time 1
SG300#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - VoIP Phone
M - Remotely-Managed Device, C - CAST Phone Port,
W - Two-Port MAC Relay
Device ID Local Adv Time To Capability Platform Port ID
Interface Ver. Live
------------------ ----------- ---- ------- ---------- ------------ -----------
SW1 gi1 2 120 R S I cisco FastEtherne
WS-C3560-8PC t0/4
SW2 gi8 2 138 R S I cisco GigabitEthe
WS-C3560C-8P rnet0/2
C-S
SG300(config)#do sh mac add
Aging time is 300 sec
Vlan Mac Address Port Type
-------- --------------------- ---------- ----------
1 00:1a:e3:73:50:05 gi1 dynamic
1 18:33:9d:03:a7:c0 gi1 dynamic
1 64:d8:14:5d:14:13 0 self
SG300(config)#do sh arp
Total number of entries: 2
VLAN Interface IP address HW address status
--------------------- --------------- ------------------- ---------------
vlan 1 1.1.1.1 00:1a:e3:73:50:40 dynamic
vlan 1 gi1 1.1.1.2 18:33:9d:03:a7:c0 dynamic
[
SW1 MAC: 00:1a:e3:73:50:40
SW2 MAC: 18:33:9d:03:a7:c0
SG300 MAC: 64:d8:14:5d:14:13
]
[SG300/3560 Spanning Tree Configuration]
SG300 does not support PVST (per vlan spanning tree) or rapid-PVST, uses MSTP to connect to Catalyst 3560 switch.
SG300 configration is the same as Catalyst switch.
spanning-tree mode mst
spanning-tree mst configuration
name TEST
Since SW1 has lowest MAC, it will be elected as ROOT.
SW2 has lower MAC than SG300, and is elected as designated for link with SG300.
SG300 Gi8 port will be blocked.
SG300#sh spanning-tree mst-configuration [25 seconds]
Gathering information ..........
Current MST configuration
Name: TEST
Revision: 0
Instance Vlans Mapped State
-------- ------------------------------------------------ -----
0 1-4094 enabled
SG300#sh spanning-tree active [15 seconds]
Spanning tree enabled mode MSTP
Default port cost method: long
Gathering information ..........
###### MST 0 Vlans Mapped: 1-20
CST Root ID Priority 32768
Address 00:1a:e3:73:50:00
The IST ROOT is the CST ROOT
Root Port gi1
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
IST Master ID Priority 32768
Address 00:1a:e3:73:50:00
Path Cost 200000
Rem hops 19
Bridge ID Priority 32768
Address 64:d8:14:5d:14:13
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Max hops 20
Name State Prio.Nbr Cost Sts Role PortFast Type
--------- -------- --------- -------- ------ ---- -------- -----------------
gi1 enabled 128.49 200000 Frw Root No P2P Intr
gi8 enabled 128.56 20000 Blk Altn No P2P Intr
----------------------------------------------------------------------------------------------------------------------------------------
SW1(config)#do sh span
MST0
Spanning tree enabled protocol mstp
Root ID Priority 32768
Address 001a.e373.5000
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
Address 001a.e373.5000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 200000 128.3 P2p
Fa0/4 Desg FWD 200000 128.5 P2p
SW2#sh span
MST0
Spanning tree enabled protocol mstp
Root ID Priority 32768
Address 001a.e373.5000
Cost 0
Port 1 (FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
Address 1833.9d03.a780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 200000 128.1 P2p
Gi0/2 Desg FWD 20000 128.10 P2p
Now let's change SG300's priority to 0 to make it ROOT
SG300(config)#spanning-tree priority 0
We can see now SG300 is root
SW1#sh span
MST0
Spanning tree enabled protocol mstp
Root ID Priority 0
Address 64d8.145d.1413
Cost 0
Port 5 (FastEthernet0/4)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768 (priority 32768 sys-id-ext 0)
Address 001a.e373.5000
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/2 Altn BLK 200000 128.3 P2p
Fa0/4 Root FWD 200000 128.5 P2p
And SW2 elected as designated switch due to its link cost to ROOT switch is better [1000M] than SW1 [100M]
We can modify interface level spanning tree parameters:
SG300(config)#int gi 1
SG300(config-if)#spanning-tree
bpdu Configure BPDU handling when STP is disabled.
bpduguard Protect network from unexpected BPDU packets
cost Change an interface's spanning tree path cost
disable Disable spanning-tree on an interface
guard Guard the interface
link-type Override the default link-type setting
mst Configure the MSTP Subsystem
port-priority Change an interface's spanning tree priority (in steps
of 16)
portfast Allow to move directly to the forwarding state when
linkup occurs
[bpdu filter]
SG300(config-if)#spanning-tree bpdu
filtering Specify that when spanning tree is disabled on the
interface, BPDU packets would be filtered.
flooding Specify that when spanning tree is disabled on the
interface, untagged BPDU packets would be flooded
unconditionally (Without applying VLAN rules), to all
ports with spanning tree disabled. Tagged BPDU packets
would be filtered.
[root guard]
SG300(config-if)#spanning-tree guard
root Guard the interface from becoming root port
SG300(config-if)#spanning-tree mst 1
cost Change an interface Spanning Tree path cost for a
specific instance.
port-priority Change an interface Spanning Tree priority (in steps
of 16) to a specific instance.
SG300(config-if)#spanning-tree link-type
point-to-point Specify that the link type of a port is point-to-point
shared Specify that the link type of a port is shared
And we can also tune spanning tree parameters:
SG300(config)#spanning-tree
bpdu Configure BPDU handling when STP is disabled.
forward-time Set a Spanning Tree FORWARD Interval
hello-time Set a Spanning Tree HELLO Interval
max-age Set a Spanning Tree MAX AGE Interval
mode Spanning tree protocol type
mst Configure MSTP Subsystem
pathcost Spanning tree path-cost method
priority Specify a Spanning Tree Priority (in steps of 4096)
<CR>
SG300(config)#spanning-tree hello-time
<1-10> Set a Spanning Tree HELLO Interval
SG300(config)#spanning-tree hello-time 1
Related Information:
Small Business 300 Series Managed Switch Administration Guide Release 1.3