Full/Half Duplex Mismatch, Unidirectional Link | D-Link DES-3250TG

D-Link DES-3250TG Standalone Layer 2 Switch

In this example, B has been elected as the designated bridge and port 2 on C is in the blocking state. The election of B as the designated bridge is determined by the exchange of BPDUs between B and C. B had a better BPDU than C. B continues sending BPDUs advertising its superiority over the other bridges on this LAN. Should C fail to receive these BPDUs for longer than the MAX AGE (default of 20 seconds), it could start to transition its port 2 from the blocking state to the forwarding state.

It should be noted: A port must continue to receive BPDUs advertising superior paths to remain in the blocking state.

There are a number of circumstances in which the STA can fail – mostly related to the loss of a large number of BPDUs. These situations will cause a port in the blocking state to transition to the forwarding state.

Full/Half Duplex Mismatch

A mismatch in the duplex state of two ports is a very common configuration error for a point-to-point link. If one port is configured as a full duplex, and the other port is left in auto-negotiation mode, the second port will end up in half-duplex because ports configured as half- or full-duplex do not negotiate.

In the above example, port 1 on B is configured as a full-duplex port and port 1 on A is either configured as a half-duplex port, or left in auto-negotiation mode. Because port 1 on B is configured as a full-duplex port, it does not do the carrier sense when accessing the link. B will then start sending packets even if A is using the link. A will then detect collisions and begin to run the flow control algorithm. If there is enough traffic between B and A, all packets (including BPDUs) will be dropped. If the BPDUs sent from A to B are dropped for longer than the MAX AGE, B will lose its connection to the root (A) and will unblock its connection to C. This will lead to a data loop.

Unidirectional Link

Unidirectional links can be caused by an undetected failure in one side of a fiber cable, or a problem with a ports transceiver. Any failure that allows a link to remain up while providing one-way communication is very dangerous for STP.

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D-Link DES-3250TG manual Full/Half Duplex Mismatch, Unidirectional Link, 159

Contents

User’s Guide Link DES-3250TG Standalone Layer 2 Switch Table of Contents Igmp SNMPV3 Link DES-3250TG Standalone Layer 2 Switch Intended Readers PrefaceVii Safety Cautions Safety InstructionsViii Safety Instructions General Precautions for Rack-Mountable Products Protecting Against Electrostatic Discharge Section Introduction Switch StackingFast Ethernet Technology Gigabit Ethernet Technology Ports Features Management Traffic Classification and Prioritization Installation Section Unpacking and SetupDesktop or Shelf Installation Unpacking Installation Power On Installing rubber feet for desktop installation Rack Installation Power Failure Power on Front Panel Section Identifying External ComponentsRear Panel Side Panels LED IndicatorsGigabit Combo Ports Link DES-3250TG Standalone Layer 2 Switch Switch to End Node Section Connecting the SwitchSwitch to Hub or Switch 10BASE-T Device Stacking vs. Standalone Operation100BASE-TX Device Managing Switch Stacks Convert a Standalone Switch to a Stacked Switch Changes to Switch Stack Structure Convert a Standalone Switch to a Stacked Switch Add a Switch to a Stack Swap a Master from a Stack Download configuration ipaddr pathfilename Stacking with DGS-3312SR DES-3250TG Switches with DGS-3312SR Command Line Console Interface Through the Serial Port Section Introduction to Switch ManagementManagement Options Web-based Management Interface Connecting the Console Port RS-232 DCE Initial screen after first connection First Time Connecting to The Switch Initial screen, first time connecting to the Switch Password Protection Creation of a new Admin level account Snmp Settings Traps IP Address AssignmentMIBs Show switch command Connecting Devices to the Switch Login to Web Manager Section Web-based Switch ManagementIntroduction User Accounts Management Admin and User Privileges User Account Management Save Changes Area Areas of the User Interface Web Pages Access Profile Table System Log Hosts PAE Access Entity Section Configuration IP Address To set the switch’s IP address Manual Default GatewayIP Address Subnet Mask Advanced Settings Switch InformationAdmin. State Click the Switch Information link in the Configuration menu Algorithm Mac Link Aggregation MAC Notification Serial Port Settings Click the Port Configuration link in the Configuration menu Port ConfigurationMAC Notification Interval MAC Notification History Size Port Configuration window Port Description State EnabledFrom and To Speed/Duplex Auto Port Mirroring Click Port Mirroring on the Configuration menu None Source PortIngress Egress Click Stack Setting on the Configuration menu Stack SettingTarget Port Status Auto MAC Address Port Range Mode Version RPS Status Static ARP Settings Igmp Snooping Igmp Query Interval Vlan ID State Static Router Ports Entry Member Ports Spanning Tree Port Transition States 802.1w Rapid Spanning TreeEdge Port P2P Port 802.1d/802.1w Compatibility STP Switch Settings Bridge Forward Delay Protocol DisabledSpanning Tree Bridge Max Age STP Port Settings 17. STP Port Settings window Priority CostMigration No Edge No Unicast Forwarding Forwarding FilteringMulticast Forwarding MAC Address Port 19. Static Multicast Forwarding Settings window VLANs on the DES-3250TG VLANsIeee 802.1Q VLANs 802.1Q Vlan Packet Forwarding 21. Ieee 802.1Q Packet Forwarding 802.1Q Vlan Tags 23. Adding an Ieee 802.1Q Tag Static Vlan Entry 25. Add 802.1Q Static Vlan window Advertisement Port Settings Tagged/None None Egress Port Vlan IdpvidForbidden Tagging and Untagging Default VlanIngress Checking 26 .1Q Port Settings window Port Bandwidth Ingress Disabled Acceptable Frame Types 27. Bandwidth Settings window Current Time Settings Sntp Settings Time Zone and DST Port Security From & To Port Security Settings Max Learning Addr.0-10 Lock Address Mode Admin StatePort Security Clear 31. Port Security Clear window Traffic Control QOS Quality of Service Parameter Description 802.1p Default Priority 33 .1p defaultpriority Settings window QOS Output Scheduling 802.1p User Priority Traffic Segmentation 36. Traffic Segmentation Setting window Link Aggregation Lacp 38. Port Link Aggregation Group window Group ID1-6 39. Port Link Aggregation Settings Add window Lacp Port 41. Link Aggregation Settings window Configuring the Access Profile Table Ethernet Part Type Profile IDSource MAC Destination MAC 802.1p Ethernet type Port 44. Access Profile Configuration IP Protocol Source IP Mask Destination IP Mask Psh Packet Content Mask 45. Access Profile Configuration window Packet Content Mask Offset Port 46. Access Rule Table window IP Mode Access IDPriority Replace Dscp Vlan Name Source IP Destination IP Dscp Protocol 48. Access Rule Display window IP 49. Access Rule Table Ethernet 802.1p Ethernet Type Priority0-7 Vlan Name Source MAC Destination MAC 51. Access Rule Display window Ethernet 53. Access Rule Configuration window Packet Content Mask Access ID Type Offset 54. Access Rule Display window Packet Content Mask 802.1x Port-Based and MAC-Based Access Control Port Access EntitySystem Log Hosts 57. The Eapol Packet Authentication Server 59. The Authentication Server Authenticator 100 Client 101 Authentication Process 102 Port-Based Network Access Control Configure Authenticator MAC-Based Network Access Control103 104 65. First 802.1X Authenticator Settings window Ctl Stat PortControl TxPeriod QuietPeriod AdmDir105 106 Port Capability Settings 107 67 .1X Capability Settings window Capability Initialize Ports for Port BasedAuth PAE State BackendState Oper Dir PortStatus Initializing Ports for MAC Based Reauthenticate Ports for Port Based109 Radius Server Reauthenticate Ports for MAC-basedAuth State 110 111 Security IP Section ManagementUser Accounts Security IP User Accounts 113 Snmp User Table 114 Snmp User Table window 115 Snmp View Table Subtree OID View NameView Type 116 117 Snmp Group Table 118 119 Snmp Community Table Snmp Host Table Access Right120 121 Snmp Engine ID CPU Utilization Section Monitoring122 Time Interval 1s Port UtilizationRecord Number Utilization Record Number Time Interval 1sShow/Hide Clear Received RX Packets125 Packets BytesView Table 126 UMB-cast RX View Line Chart127 Multicast UnicastBroadcast 128 View Table Transmitted TX129 130 Tx Packets Analysis window table for Bytes and Packets 131 Errors UnderSize CrcErrorOverSize Fragment Drop JabberShow/Hide Clear LateColl ExDefer134 Packet Size Size135 128-255 65-127256-511 136 512-1023 MAC Address1024-1518 137 138 15. MAC Address Table window Find ARP TableLearned Next 140 Igmp Snooping Group 141 Igmp Snooping Forwarding 142 Vlan Status Authenticator Status Port Access ControlRouter Port 143 144 21. Authenticator Status window Tftp Utilities Section MaintenanceDownload Firmware from Server 145 Upload Settings to Tftp Server Download Settings from Tftp ServerUpload Log to Tftp Server 146 Ping Test Switch History147 148 Reboot Services Reset RebootReset System 149 Reset Config Technical SpecificationsAppendix a Logout 151 Physical and Environmental 152 Performance Blocking State Appendix BPort in the blocking state does the following 153 Port in the listening state does the following Listening State Port in the learning state does the following Learning State155 Port in the forwarding state does the following Forwarding State Disabled port does the following Disabled State157 Troubleshooting STP Spanning Tree Protocol Failure Unidirectional Link Full/Half Duplex Mismatch159 Packet Corruption Resource ErrorsIdentifying a Data Loop 161 Warnung Warranty and RegistrationPrecaución Attenzione Warranty and Registration Information Warranties Exclusive Page Page Product Registration Link Europe Limited Product Warranty Page Link Europe Limited Produktgarantie Link Europe a limité la garantie des produits Garante Link Europe Termini di Garanzia dei Prodotti Link International Offices All Countries and Regions excluding USA Registration Card