FS S3150-8T2FP User manual

POE+ Series Switches Loopback
Detection Configuration Guide
Models: S3150-8T2FP
S3260-8T2FP
S3260-16T4FP
S3400-24T4FP
S3400-48T4SP

POE+ SERIES SWITCHES LOOPBACK DETECTION CONFIGURATION GUIDE
Contents
1. Loopback Detection Configuration...................................................................................................................................................... 1
1.1 Introduction to Loopback Detection...................................................................................................................................................1
1.1.1 Format of Loopback Detection Packet.......................................................................................................................................1
1.2 Loopback Detection Configuration Task List...................................................................................................................................... 2
1.3 Loopback Detection Configuration.....................................................................................................................................................2
1.3.1 Configuring Global Loopback Detection................................................................................................................................... 2
1.3.2 Configuring Loopback Detection of the Port.............................................................................................................................2
1.3.3 Configuring Loopback Detection for Certain VLANs................................................................................................................. 2
1.3.4 Configuring Loopback Detection Time......................................................................................................................................2
1.3.5 Configuring Loopback-Detection Control................................................................................................................................. 3
1.3.6 Configuring Loopback Detection Destination MAC.................................................................................................................. 3
1.3.7 Configuring Loopback Detection Existence.............................................................................................................................. 3
1.3.8 Configuring the Upper Threshold the Loop Detection Frame Received Every Minute............................................................4
1.3.9 Configuring to Enable or Disable Frame Number Detection Function.....................................................................................4
1.3.10 Showing Loopback Detection Global Configuration Information.......................................................................................... 4
1.3.11 Showing Loopback Detection Interface...................................................................................................................................4
1.4 Configuration Example........................................................................................................................................................................ 4

POE+ SERIES SWITCHES LOOPBACK DETECTION CONFIGURATION GUIDE
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1. Loopback Detection Configuration
1.1 Introduction to Loopback Detection
Loopback in the network may cause the equipment repeatedly forward the broadcast, multicast and unknown unicast, resulting in
the waste of network resources or the network breakdown. In order to timely inform the user the conditions of the network
connection and configuration, a detection mechanism is necessary. So, there is the Loopback Detection. It can detect if there is a
loopback in the port of the equipment, i.e. forward packets from the port regularly and detect whether the packets are sent back
from the forwarding port. If there is a loopback in the port, Loopback Detection will forward the warning information timely to the
network management system. Thus, the equipment can avoid long-time off-line. Besides, the equipment supports three modes of
port controls: block, no MAC learning, and shutdown (error-disable).
The OLT supports:
the loopback detection of the port;
the destination MAC address of the loopback detection packet; the loopback detection packet forwarded by each port can
be configured;
the loopback detection for certain VLANs (at most 10);
the loopback-detection hello-time and loopback-detection recovery-time;
three modes of port controls: block, no MAC learning, and shutdown (error-disable);
loopback detection existence configuration.
1.1.1 Format of Loopback Detection Packet
Field
Length/Byte
Value
DMAC
6
0x0180C2B0000A (Default, can be
configured)
SMAC
6
MAC address of OLT system
TPID
2
0x8100, VLAN tag type
TCI
2
The concrete value of VLAN tag, priority,
VLAN ID
TYPE
2
Type: Protocol type, value 0x9001
CODE
2
The subtype of the protocol, represents
loopback detection, value 0x0001
VERSION
2
0x0000, reserve at present
Length
2
0x0008, the length of the loopback
detection packet head
RESERVE
2
Reserve the field
SYSMAC
6
MAC address of OLT system
SEQUENCE
4
Serial number of the packet, it will be
automatically generated before forwarding
the packet
DiID
4
Port number, the 85 product is global port
number
End
2
0x0000 end mark

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1.2 Loopback Detection Configuration Task List
Configuring Global Loopback Detection
Configuring Loopback Detection of the Port
Configuring Loopback Detection for Certain VLANs
Configuring Loopback Detection Time
Configuring Loopback-Detection Control
Configuring Loopback Detection Destination MAC
Configuring Loopback Detection Existence
Configuring the Upper Threshold the Loop Detection Frame Received Every Minute
Configuring to Enable or Disable Frame Number Detection Function
Showing Loopback Detection Global Configuration Information
Showing Loopback Detection Interface
1.3 Loopback Detection Configuration
1.3.1 Configuring Global Loopback Detection
Enable or disable the global loopback detection. The global commands are invalid for all physical ports. The loopback detection will
take effect only when enabling the global loopback detection. The port configuration is invalid if the loopback detection disables.
Command
Purpose
[no] loopback-detection
Configure the global loopback detection.
1.3.2 Configuring Loopback Detection of the Port
This command can be used to enable or disable loopback detection on a specified port. However, this settings takes effect only after
loopback detection is enabled globally.
Command
Purpose
[no] loopback-detection enable
Configuring Port Loop Check
1.3.3 Configuring Loopback Detection for Certain VLANs
After loopback detection is configured on a specified VLAN, the port transmits multiple detection packets of specified VLAN tag
regularly and the number of these detection packets transmitted by this port can be up to 10.
Note that: The port must be in the configured VLAN and the VLAN must be created, or the configuration is invalid. Specifically, if the
port configures the loopback detection to the runk mode in VLAN2-VLAN8 and trunk vlan-allowed is VLAN 5-8, packets with 2-4tag
from OLT cannot be forwarded through the port and the configuration is invalid. Meanwhile, configure trunk vlan-untagged to 2-8,
so that the forwarded packets with vlan tag. The relevant VLAN must be created, or the tag with VLAN id will be invalid.
Command
Purpose
[no] loopback-detection vlan-control vlanlist
Configure the loopback detection for certain VLANs
1.3.4 Configuring Loopback Detection Time
Command
Purpose
[no] loopback-detection hello-time time
Configure loopback-detection recovery-time
As the network is in change, the loopback detection is a lasting process. The port forwards loopback detection packets regularly. The
time interval, i.e. loopback-detection hello-time is 3 seconds in default.

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Command
Purpose
[no] loopback-detection recovery-time time
Configure loopback-detection recovery-time
Configure the recovery time after the loopback is disappeared. The loopback is regarded to be disappeared if the port doesn’t
receive the forwarded loopback detection packet in 10s. It is recommended that the recovery time is at least 3 times of the packet
forwarding time and the recovery time is more than 10s than the hello-time.
1.3.5 Configuring Loopback-Detection Control
Command
Purpose
[no] loopback-detection control {block | learning | shutdown}
Configure loopback detection control
If there is a loopback in the network, control the port by command [no] loopback-detection control. The port has three controlled
modes: block, no MAC learning, shutdown (error-disable). The trap warning information will be forwarded no matter what control
mode is configured. The trap configuration is by default.
After loopback detection is enabled globally, the port on which loopback detection is enabled transmits the loopback detection
packets and receives the already transmitted loopback detection packets. Four control actions are conducted on the port:
Block: When detecting the loopback, the port will be isolated from other ports and the data forwarded into the port cannot be
forwarded to other ports. When the port is in the state of protocol down, the MAC address table will age simultaneously.
Nolearn: Prohibit port MAC learning. When detecting the loopback, the port will have no MAC learning but the MAC address table
ages.
Shutdown: Disable the port. When detecting the loopback, the port forwards trap warning information, ages the MAC address table
and automatically disables the port (error-disable). Thus, the port cannot forward the packet until the error-disable-recover time.
Trap: The port only report warning. When detect the loopback, the port only reports warning and ages MAC address. The default
controlled configuration of the port is trap.
When the port is in block, the packet will not be forwarded into it and the port will continue forward the loopback detection packet.
When the loopback disappears in detection, the port will automatically recover. By default, if the forwarded loopback detection
packet is not received in 10s, the loopback will be regarded as disappeared. In block, the port protocol is down; in shutdown, the
port link is directly down.
1.3.6 Configuring Loopback Detection Destination MAC
Command
Purpose
[no] loopback-detection dest-mac Mac-address
Configure the loopback detection dest-mac address
The default loopback detection destination mac is 01-80-C2-00-00-0a. If the user has configured, the MAC address configured by the
user will be taken as the destination mac address.
1.3.7 Configuring Loopback Detection Existence
Command
Purpose
[no] loopback-detection existence
Configure loopback detection existence
This command is mainly used to solve the problem that loopback exists on a port or not when this port is up and its loopback
detection function takes effect. When the controlled action of this port is set to shut down, it is improper to regard that loopback
exists on this port for a shutdown port has already not forwarded packets. There is no loopback by default.

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1.3.8 Configuring the Upper Threshold the Loop Detection Frame Received Every Minute
Command
Purpose
[no] loopback-detection frames-threshold frames-threshold
Configures the upper threshold the loop detection frame received
every minute.
Configures the upper threshold the loop detection frame received every minute. The default value is 10.
1.3.9 Configuring to Enable or Disable Frame Number Detection Function
Command
Purpose
[no] loopback-detection frames-monitor
Configures to enable or disable frame number detection function
Configures to enable or disable frame number detection function
1.3.10 Showing Loopback Detection Global Configuration Information
Command
Purpose
show loopback-detection
Show global loopback detection configuration
It is mainly used for showing global loopback detection information, including global configuration, loopback existence and some
configuration information.
1.3.11 Showing Loopback Detection Interface
Command
Purpose
show loopback-detection interface intf
Show loopback detection interface
It is mainly used for showing loopback detection information, including the timer value and the packet information.
1.4 Configuration Example
Figure 1.1 Loopback Detection Configurations
As shown in Figure 1.1, port OLT S1 designates loopback detection of certain VLAN (1,2,3):
Switch S1:
Configure interface GigaEthernet0/1:
switchport trunk vlan-untagged 1-3
switchport mode trunk
loopback-detection enable
loopback-detection control block
POE+ SERIES SWITCHES LOOPBACK DETECTION CONFIGURATION GUIDE

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loopback-detection vlan-control 1-5
Global Configuration:
loopback-detection
vlan 1-3
Switch S2:
Configure interface GigaEthernet0/1:
switchport mode trunk
Configure interface GigaEthernet0/2:
switchport mode trunk
Configure interface GigaEthernet0/3:
switchport mode trunk
Global Configuration:
vlan1-3
Switch S3:
Configure interface GigaEthernet0/1:
switchport pvid 3
If S3 has loopback and PVID of the port is 3, the packets will forward back to G5/1 of S1. S1 will block G5/1 if there is loopback.

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