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Merge pull request sonic-net#63 from sandeep-kulambi/rpvst_loopguard
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RPVST - Loop guard functionality support
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@NarendraBandarupalli
NarendraBandarupalli authored Sep 17, 2020
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102 changes: 87 additions & 15 deletions L2/STP/SONiC RPVST Plus FS.md
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Expand Up @@ -49,6 +49,7 @@ RPVST+.
| Rev | Date | Author | Change Description |
| --- | ----------- | -------------------- | --------------------------------- |
| 0.1 | 06/07/2019 | Gunavardhani Bandaru | Initial version |
| 0.2 | 07/27/2020 | Sandeep Kulambi | Add loop guard details |

<a name="References"></a>
# References
Expand Down Expand Up @@ -95,6 +96,7 @@ This document describes the high level design of RPVST+ feature in SONiC.
- DA MAC in case of RPVST+ should be Cisco Shared Spanning Tree Protocol Address 01:00:0C:CC:CC:CD
- Support protocol operation on static breakout ports
- Support protocol operation on physical and Port-channel interfaces
- Support loop guard functionality

<a name="12-config-mgmt-reqmts"></a>
## 1.2 Configuration and Management Requirements
Expand Down Expand Up @@ -132,7 +134,7 @@ RPVST+ is IEEE 802.1w (RSTP) standard implemented per VLAN. A single instance of
- Alternate - Provides the best alternate path to the root bridge when the root port goes down
- Backup - Provides a redundant path to the same network segment. The purpose of Alternate and Backup ports is to provide connectivity when other network components fail.
- Disabled - Has no role in the topology

- Allows ports that are configured as Edge ports to be present in an RPVST+ topology. Edge ports are ports of a switch that are connected to work stations or computers. Edge ports do not register for any incoming BPDU related events. RSTP does not consider edge ports in the spanning tree calculations. Hence, any port flaps on edge ports do not cause spanning tree topology changes.

- Supports the following bridge port states:
Expand Down Expand Up @@ -168,6 +170,7 @@ Following config DB schemas are defined / modified for supporting this feature:
;Status: work in progress
key = STP|GLOBAL ; Global STP table key
mode = "rpvst" ; spanning-tree mode - "pvst" or "rpvst"
loop_guard = "true/false" ; Enable/disable global loop guard


"rpvst" is added as one of the modes to existing STP_GLOBAL_TABLE.
Expand All @@ -179,6 +182,7 @@ Following config DB schemas are defined / modified for supporting this feature:
key = STP_INTF|ifname ; ifname with prefix STP_INTF, ifname can be physical or port-channel name
edge_port = BIT ; enabled or disabled. If set to enabled, then the port becomes an edge port in the domain.
link_type = "link_type" ; auto, point-to-point or shared link type.
loop_guard = "true/false/none" ; Enable/disable loop guard on interface, none - disable global loop guard configuratio on interface

The following fields are added to existing STP_INTF_TABLE - edge_port and link_type.

Expand All @@ -194,6 +198,13 @@ The following fields are added to existing STP_INTF_TABLE - edge_port and link_t

The following fields are added to existing STP_INTF_TABLE - edge_port and link_type.

#### STP_VLAN_PORT_TABLE ####

;Stores STP VLAN port details
;Status: work in progress
key = STP_VLAN_PORT:"Vlan"vlanid:ifname ; VLAN+Port with prefix "STP_VLAN_PORT"
port_state = "state" ; STP state - disabled, block, listen, learn, forward, root-inc, loop-inc, bpdu-dis

#### STP_VLAN_INTF_FLUSH_TABLE ####

;Defines vlan and port for which flush needs to happen
Expand All @@ -202,7 +213,7 @@ The following fields are added to existing STP_INTF_TABLE - edge_port and link_t
state = "true" ; if true - perform flush.

New table STP_VLAN_INTF_FLUSH_TABLE is created as stated above.

<a name="33-switch-state-service-design"></a>
## 3.3 Switch State Service Design

Expand All @@ -217,7 +228,7 @@ All STP operations for programming the HW are be handled as part of OrchAgent. O
Orchagent listens to updates related to flush per port per vlan on APP DB. When flush per port per vlan request is set due to topology change, Orchagent performs FDB/MAC flush for the vlan and the port.

* FDB/MAC flush - STP_VLAN_INTF_FLUSH_TABLE

### 3.3.2 Other Process

Please see SONIC PVST+ Functional specification for more details.
Expand Down Expand Up @@ -274,7 +285,7 @@ The 255 VLANs are selected in the following order:

2) Only one mode can be enabled at any given point of time.


#### 3.6.2.1.2 Per VLAN spanning-tree ####

This command allows enabling or disabling spanning-tree on a VLAN. Use this command to disable or enable PVST / RPVST+ on a VLAN. Changing the PVST+ / RPVST+ state in a VLAN affects only that VLAN. This command enables PVST+ / RPVST+ for all ports in a VLAN.
Expand Down Expand Up @@ -369,6 +380,26 @@ This command allows configuring the bridge priority in increments of 4096 (defau

**Command Mode**: Global Config

#### 3.6.2.1.7 Loop guard ####

This command allows configuring the loop guard on all the ports.

By default, when spanning-tree stops receiving the BPDUs on a blocking port, it transitions to forwarding state which can result in a loop in the network. Loop guard feature when enabled, avoids this transition of non-designated ports to forwarding state and instead moves the port to a loop inconsistent state where the port continues to block the traffic to avoid the loop.

**spanning-tree loopguard default**

**no spanning-tree loopguard default **

**Syntax description**:

| Keyword | Description |
| ----------------- | --------------------------------------------- |
| loopguard default | Enable loop guard by default on all the ports |

**Default**: Global loop guard is disabled

**Command Mode**: Global Config

### 3.6.2.3 VLAN, interface level

Below configurations allow STP parameters to be configured on per VLAN, interface basis.
Expand Down Expand Up @@ -432,7 +463,7 @@ This command allows enabling or disabling of STP on an interface.
**spanning-tree enable **

**no spanning-tree enable **

**Syntax description**:
This command has no arguments or keywords.

Expand Down Expand Up @@ -480,15 +511,36 @@ Can be set to point-to-point or shared. Port is connected to another port throug

**Command Mode**: Interface Config

### 3.6.2.4.4 Guard type

This command allows configuring loop guard or root guard on an interface.

**spanning-tree guard {loop | root | none}**

**no spanning-tree guard**

**Syntax description**:

| Keyword | Description |
| ------- | ------------------------------------------------------------ |
| loop | Enable loop guard on the interface |
| root | Enable root guard on the interface |
| none | Disable both loop guard and root guard on the interface. This option allows loop guard to be disabled on an interface even while global level loopguard is enabled. |

**Default**: Both loop guard and root guard are disabled on the interface

**Command Mode**: Interface Config

<a name="363-show-commands"></a>

### 3.6.3 Show Commands

#### 3.6.3.1 Show spanning-tree vlan ####

Display spanning-tree information on the given vlan.

**show spanning-tree vlan <vlan\>**

Syntax Description:

| Keyword | Description |
Expand All @@ -507,17 +559,17 @@ Example:
Identifier MaxAge Hello FwdDly Hold
hex sec sec sec cnt
0001000480a04000 20 2 15 3

RootBridge RootPath DesignatedBridge Root Max Hel Fwd
Identifier Cost Identifier Port Age lo Dly
hex hex sec sec sec
0001000480a04000 0 0001000480a04000 Root 20 2 15

RSTP (IEEE 802.1w) Port Parameters:
Port Prio PortPath link Edge BPDU Role State Designa- Designated
Num rity Cost type Port Filter ted cost bridge
Ethernet3 128 20000 P2P F N DISABLED DISABLED 0 0000000000000000
Ethernet13 128 20000 P2P F N DISABLED DISABLED 0 0000000000000000
Port Prio PortPath link Edge BPDU Guard Role State Designa- Designated
Num rity Cost type Port Filter Type ted cost bridge
Ethernet3 128 20000 P2P F N Loop DISABLED DISABLED 0 0000000000000000
Ethernet13 128 20000 P2P F N - DISABLED DISABLED 0 0000000000000000

#### 3.6.3.2 show spanning-tree counters vlan ####

Expand Down Expand Up @@ -545,10 +597,23 @@ Example:
PortChannel15 20 6 4 1 4 2

Note:
- TCN Tx / Rx counters are not applicable for RPVST+
- TCN Tx / Rx counters are not applicable for RPVST+
- In RPVST+ mode, Config BPDU TX / RX counters will get updated only upon receiving STP BPDUs.

<a name="364-debug-commands"></a>

-show spanning-tree inconsistentports
This command displays the root inconsistent and loop inconsistent ports

```
Root guard timeout: 120 secs
Loop guard default: Enabled
PortNum VLAN Inconsistency State
-------------------------------------------------
Ethernet8 100 Loop Inconsistent
```

### 3.6.4 Debug Commands

Following is a common debug command for PVST+ / RPVST+
Expand All @@ -564,9 +629,9 @@ Following clear commands will be supported
- clear spanning-tree counters
- clear spanning-tree counters vlan <vlan-id>
- clear spanning-tree counters vlan <vlan-id> interface <ifname>
- clear spanning-tree counters interface <ifname>
- clear spanning-tree counters interface <ifname>

- clear spanning-tree detected-protocol [interface {ethernet <ifname> | port-channel <port-channel-id>}]
- clear spanning-tree detected-protocol [interface {ethernet <ifname> | port-channel <port-channel-id>}]
Use this command to restart protocol migration on a given interface. Applied to all ports when interface is not specified.

<a name="366-rest-api"></a>
Expand Down Expand Up @@ -634,6 +699,7 @@ Warm boot is not supported.
34) Verify CLI to display spanning-tree counters
35) Verify CLI to display BPDU guard port information
36) Verify CLI for clear spanning tree counters
37) Verify global and interface level loop guard CLIs


**Functionality:**
Expand Down Expand Up @@ -675,6 +741,12 @@ Warm boot is not supported.
36) Verify bridge id encoding includes the VLAN id of the respective RPVST+ instance
37) Verify RPVST+ operational data is sync to APP DB
38) Verify RPVST+ over static breakout ports
39) Verify global loopguard functionality, stop the BPDUs on blocking port and verify the port moves to loop inconsistent state
40) In above test case, resume BPDU reception and verify port moves back to its original state, i.e. root forwarding or alternate blocking.
41) Verify interface loopguard functionality
42) Verify configuring guard option as none disables both root guard and loop guard, and also when global loop guard is enabled, port level loop guard is disabled




**Scaling**
Expand Down

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