Loopback Detection Configuration I Table of Contents Table of Contents Chapter 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..............................................................3 1.3.3 Configuring Loopback Detection for Certain VLANs................................................ 3 1.3.4 Configuring Loopback Detection Time........................................................................3 1.3.5 Configuring Loopback-Detection Control................................................................... 3 1.3.6 Configuring Loopback Detection Destination MAC.................................................. 4 1.3.7 Configuring Loopback Detection Existence............................................................... 4 1.3.8 Configuring the Upper Threshold the Loop Detection Frame Received Every Minute......................................................................................................................................... 5 1.3.9 Configuring to Enable or Disable Frame Number Detection Function..................5 1.3.10 Showing Loopback Detection Global Configuration Information......................... 5 1.3.11 Showing Loopback Detection Interface.................................................................... 5 1.4 Configuration Example..............................................................................................................5 II Loopback Detection Configuration Chapter 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 1 Loopback Detection Configuration 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 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. 2 Loopback Detection Configuration 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. 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 3 Loopback Detection Configuration [no] loopback-detection control Configure loopback detection control {block|learning|shutdown} 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 state 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 Configure the loopback detection dest-mac Mac-address 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 shutdown, 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. 4 Loopback Detection Configuration 1.3.8 Configuring the Upper Threshold the Loop Detection Frame Received Every Minute Command Purpose [no] loopback-detection frames-threshold Configures the upper threshold the loop frames-threshold 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 5 Loopback Detection Configuration 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 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. 6