Cabletron Systems SSIM-H2-02 manual Preventing Frame Looping

Page 28

19

In a pure Token Ring network, an All Routes Explorer (ARE) frame generated from Station A traverses all rings only one time based on a Routing Information Field (RIF) expanded by each source-routed bridge. In this example, both translational links are in the forwarding state. An ARE frame originating in Ring1 may go through the Ethernet cloud and come back to Ring2. Because the RIF is lost when passing through the Ethernet cloud, LAN segment 1 is no longer included in the new RIF and the frame will be forwarded by Bridge1 from Ring2 back to Ring1. This results in frame duplication – after visiting Ring1 again, the frame will be discarded by the switch connected to Ring1.

This issue can be resolved by making sure that only one translational link can be in the forwarding state.

Preventing Frame Looping

The network presented in Figure 6 was free of the ARE looping issue because the entire the Ethernet cloud had the same LAN Segment number – each switch had the same number for its Ethernet ports.

In Figure 7, the switches have different LAN segment numbers for Ethernet ports (3 and 4). In this configuration, an infinite loop is created in addition to the frame duplication issue.

Station A sends an ARE frame to Ring1, for example IP ARP with destination MAC being Broadcast. This frame is converted to a transparent broadcast and sent on Ethernet link 1. The frame is then received by the switch on link 2 and sent as an ARE frame to Ring 2 – note that the RIF does not contain LAN Segment 4. The ARE frame is then forwarded by Bridge 1 and switch link 1 back to the Ethernet, and so on.

Figure 7. Frame Looping

SSIM-H2-02 Fast Ethernet - Translational Switch SmartStack Interface Module Installation and User Guide

Configuration

Image 28
Contents Page Order Number 9032962-01 OC-7063 v .1 Vcci Notice FCC NoticeIndustry Canada Notice Iii Declaration of Conformity AddendumApplication of Council Directives 89/336/EEC 73/23/EEC Page Table of Contents Statistics List of Figures ViiList of Tables ViiiSSIM-H2-02 Switch SmartStack Interface Module IntroductionFeature Description This makes it possible to configure the device Part of the LAN switchSnmp is supported via the host processor Processor on the SmartStack STS16-20RMMIB Support FEUplink MIBInstallation Package ContentsInstallation Procedure Hardware Installation Removing the Expansion Slot CoverSoftware Installation Tftp DownloadSerial Download From the main menu, select Download→ UploadCabling LEDsPower-On Self Test Configuration Default ConfigurationConfiguration Introduction Ports, Port Groups and VLANsVirtual Port Restriction TS Virtual Ports and Vlan TaggingRing Number Restriction Source Routed Transparent Bridging SRT Mode Source Routed Switching SRS Operation ModeBridging Modes Source Routed Bridging SRB Mode Ethernet CRF in SRB Bridging ModeNetwork Scenarios Redundant Connections to Fast Ethernet NetworkPreventing Frame Duplication Preventing Frame Looping Frame LoopingSpanning Tree Configuration Broken Ethernet CloudRedundant Connections to Fast Ethernet Network Page Technical Background STP Cost Modification General Guidelines Main Switch Menu Navigating Within the MenusConfiguration Overview Vlan Configuration Port Configuration TS PortsBRF Configuration Local Vlan Port ConfigurationVirtual Port Configuration StatusDisplay only. Shows the current status of the port Address Demand Aging LevelDefault Display only. Shows the current status of the virtual portYou can use only one value as MTU 1558 001Vlan Tagging Mode FC ModificationAddress Aging Time RIF Not Learn IntervalIP Conversion Status Frame Conversion ConfigurationIP Conversion Parameters Change Default SR IP Ethernet FormatSets the format of IP frames on Ethernet Snap Frame in the Ieee 802.3 format with SnapEnable IP Fragmentation Novell Conversion StatusExplorer Frames Type TR MAC Address for IP MulticastsNovell Conversion Parameters Change Novell Frames ConversionNovell Token Ring Format Novell Ethernet FormatNetBios Conversion Status NetBios Conversion Parameters ChangeNetBios Frames Conversion IPX Address TranslationNetBios Token Ring Format NetBios Ethernet FormatSNA Conversion Status SNA Conversion Parameters ChangeSNA Ethernet Format Sets the format of SNA frames on EthernetOther Frames w/SNAP Conversion Status Other Frames w/SNAP Conversion Parameters ChangeOther Frames w/SNAP Frames Conversion Other Frames w/SNAP Token Ring FormatOther Frames w/o Snap Conversion Status Other Frames w/SNAP Ethernet FormatOther Frames w/o Snap Conversion Parameters Change Other Frames w/o Snap Frames ConversionOther Frames w/o Snap Token Ring Format Other Frames w/o Snap Ethernet FormatDual Home FEP Addresses Configuration Page Statistics Statistics Menu Port Status Port Statistics General StatisticsDiscarded Frames Table Filtered by Address Filter Table Filtered by Dsap FilterLocally Filtered Table Blocked Virtual PortTraffic Counters Error Counters Virtual Port Statistics Discarded Frames StatisticsVirtual Port State Frames ForwardedNetBios Inbound Translation errorsOther w/SNAP Other w/o SnapOutbound Translation Errors Outbound No TranslationFragmentation Error Generic w/o SnapGetting in Touch with Technical Support Your email addressPage Appendix A. Abbreviations Service Access Point Sub-Network Access ProtocolSource Route Switching Translational SwitchIndex Index-1Local Vlan port configuration Index-2710001816