AX Series L2 Loop Detection Configuration Guide Edition 2 Copyright © 2008, 2010, ALAXALA Networks Corporation. All rights reserved.
AX Series L2 Loop Detection Configuration Guide (Edition 2) Preface The AX Series L2 Loop Control Guide is intended to help system engineers grasp the operational overview of each functionality, system configuration, and stable operation by providing them with technical information for system configurations using each functionality related to L2 looping (Auto MDI/MDI-X suppression, L2 loop detection, and storm control) supported by the AX series (AX6700S/AX6600S/AX6300S, AX3600S, AX2400S, and AX1200S).
AX Series L2 Loop Detection Configuration Guide (Edition 2) Revision history Edition Rev. Date Description Edition 1 Edition 2 --- July 17, 2008 Feb. 17, 2010 First edition Preface The version of the used device has been updated. Introduction to and usage example of the L2 loop monitoring tool have been added. Notes on using the AX6600S series have been added. Appendix Configuration File has been updated. Copyright © 2008, 2010, ALAXALA Networks Corporation. All rights reserved.
AX Series L2 Loop Detection Configuration Guide (Edition 2) Contents 1. 2. 3. Impact of an L2 Loop and the Countermeasure Functionality...........................................................5 1.1 L2 loops and their risks ...............................................................................................................5 1.2 L2 loop control functionality.........................................................................................................6 1.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 1. Impact of an L2 Loop and the Countermeasure Functionality 1.1 L2 loops and their risks Networks are generally based on an assumption that the terminals and servers that send and receive data are connected on an end-to-end basis both physically and logically.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 1.2 L2 loop control functionality The AX series has the following functionality for preventing L2 loops: Auto MDI/MDI-X suppression Prevents L2 loops by creating no link-ups even with incorrect connections between access ports. This is applicable only to twisted pair straight cables. L2 loop detection functionality Prevents L2 loops by detecting L2 loops in a device and blocking the port.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 1.4 (1) L2 loop detection functionality Functionality overview The L2 loop detection functionality is used to detect a loop failure in a Layer 2 network and correct the loop failure by blocking the port that caused the loop.
AX Series L2 Loop Detection Configuration Guide (Edition 2) (2) Operation In L2 loop detection, an L2 control frame for detecting an L2 loop (an L2 loop detection frame) is sent regularly from the port (a physical port or a channel group) specified in the configuration section. If the frame returns to the sending device, the functionality determines that a loop failure has occurred. Switch Receipt of L2 loop detection frame -> Detection of L2 loop Sending L2 loop detection frame Small-scale hub, etc.
AX Series L2 Loop Detection Configuration Guide (Edition 2) (4) Transmission rate and sending interval of L2 loop detection frames The L2 loop detection functionality works when the target device sends and receives an L2 loop detection frame. However, the transmission rate of L2 loop detection frames required for each device is determined based on the sending interval of L2 loop detection frames and the number of VLAN ports subject to L2 loop detection.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 1.5 (1) Storm control Functionality overview Storm control refers to the functionality that limits the number of flooded frames that are forwarded by a switch to control the impact of storms on the network and connected devices.
AX Series L2 Loop Detection Configuration Guide (Edition 2) Table 1.5-2 Configurations related to storm control (AX3600S/2400S/1200S series) Parameter Description Configured in interface configuration mode (config-if) storm-control broadcast level pps Enables storm control for broadcast frames and sets the threshold value for the receiver bandwidth for storm control. Frames exceeding the threshold are discarded.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 2. Examples of the Basic Usage of the L2 Loop Detection Functionality The efficient use of each functionality for preventing L2 loops can stop the occurrence of L2 loops or reduce the impact of L2 loops to a minimum, if they occur. This chapter specifically describes examples of the basic configurations and operations of the L2 loop detection functionality. 2.
AX Series L2 Loop Detection Configuration Guide (Edition 2) The following figure shows an example of a node of an access switch where the L2 loop detection functionality is set. (Option) Upstream network of STP (Rapid PVST+) SNMP manager IP address of Switch 192.168.10.1 (VLAN 10) 0/1 0/2 VLANs E1: AX2430S-24T VLAN 10 0/5 0/6 AX-NU (L2 loop monitoring tool) 192.168.100.100 Empty (not to be added) 192.168.100.200 public VLAN 11 0/7 0/8 0/9 VLAN 12 ...
AX Series L2 Loop Detection Configuration Guide (Edition 2) 2.2 Important points for constructing a system (1) Set the L2 loop detection functionality on a device located as near as possible to the endpoint, such as an access switch. As described above: - L2 redundancy protocols are used as measures against loops on upstream networks such as core networks in many cases. - When a port is blocked due to loop detection, devices located further upstream have more impact on downstream networks.
AX Series L2 Loop Detection Configuration Guide (Edition 2) (6) When using STP, enable PortFast and the BPDU filter for access ports for which the L2 loop detection setting is enabled. When STP is used for the L2 redundancy protocol, the functionality related to ports on the endpoint side include PortFast, BPDU guard, and the BPDU filter. If the functionality is used with the L2 loop detection functionality, ALAXALA Networks Corporation recommends that PortFast and the BPDU filter be enabled.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 2.3 Configuration example The following table provides configuration examples of important points for constructing a system. For details about overall configuration, see the Appendix. (1) Configuring an access edge node Configuring E1 Configuring STP (config)# spanning-tree mode rapid-pvst (config)# spanning-tree portfast default Use Rapid PVST+ for the connection with the upstream network. The PortFast functionality is used by default.
AX Series L2 Loop Detection Configuration Guide (Edition 2) Configuring E1 Configuring an SNMP trap destination (config)# snmp-server host 192.168.100.200 traps "public" loop-detection Set the host address and community name of the SNMP manager to which traps related to the L2 loop detection functionality are issued. Configuring a device IP (config)# interface vlan 10 (config-if)# ip 192.168.10.1 255.255.255.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 2.4 Troubleshooting with operation commands This section describes the basic operations of the L2 loop detection functionality in the configuration example. When the L2 loop detection functionality detects an L2 loop, the detection of a loop is output in the message log of the device and a log entry is recorded. It is also possible to issue an SNMP trap.
AX Series L2 Loop Detection Configuration Guide (Edition 2) (1) Detection of the L2 loop status via message logs, show logging, and SNMP traps When an L2 loop is detected and the port is blocked due to this loop, message logs are displayed as shown below. These logs can be viewed also in the log message history shown by the show logging command. Display example E1>sh logging ... EVT 06/26 17:19:57 E4 VLAN 20800001 0700:000000000000 L2LD : Port(0/24): inactivated because of loop detection from port(0/24).
AX Series L2 Loop Detection Configuration Guide (Edition 2) (2) Identification of loop location with the show loop-detection command The status of L2 loops can be checked mainly with the show loop-detection command.
AX Series L2 Loop Detection Configuration Guide (Edition 2) A loop is created by connecting two ports on an intermediate device (such as a hub) belonging to the switch device. 0/5 - Connecting ports on a hub under the device In this case, using the show loop-detection command results in the following display: >show loop-detection ...
AX Series L2 Loop Detection Configuration Guide (Edition 2) (3) Restoring (activating) blocked ports and removing the loop status display After taking measures against the L2 loop status, restore blocked ports and remove the loop status display. Follow the procedures below. (i) Restoring the blocked ports Use the show port command to confirm that the blocked port is in the inact status and then activate the port.#1 (ii) Checking the loop status display Execute the show loop-detection command.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 2.5 Other operation commands This section describes other operation commands related to the L2 loop detection functionality. For details about operation commands, see the manual Software Manual Operation Command Reference Vol. 1 for each device. (1) show loop-detection logging Displays the L2 loop detection log entries with the L2 loop detection functionality.
AX Series L2 Loop Detection Configuration Guide (Edition 2) 3. Restrictions and Notes 3.1 For Auto MDI/MDI-X suppression This functionality is enabled when auto-negotiation is specified. This functionality is disabled when 1000BASE-X is used as the interface and sfp is specified for media-type. This functionality is unavailable when 10GBASE-R is used as the interface. 3.
AX Series L2 Loop Detection Configuration Guide (Edition 2) Table 3.
AX Series L2 Loop Detection Configuration Guide (Edition 2) Appendix: Configuration File This file shows examples of configurations described in this guide. The text file attached to this file contains all of the configurations for each device in each network configuration described in Chapter 2. (Extracting the attachment file requires Adobe Acrobat 5.0 or later or Adobe Reader 6.0 or later.) For details about each configuration, see the attachment with the same name as shown below. 2.
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