About VLANs | 3Com 2500 specification

About VLANs

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Default VLAN When you start up the LANplex system, the system automatically creates a VLAN interface called the default VLAN. Initially, the default VLAN includes all of the switch ports in the system. In the LANplex system, the default VLAN serves to deﬁne:

■The ﬂood domain for protocols not supported by any VLAN in the system

■The ﬂood domain for protocols supported by a VLAN in the system but received on nonmember ports

Both cases represent exception ﬂooding conditions that are described in the following sections.

Modifying the Default VLAN

New switch ports can dynamically appear in the LANplex system if you insert a daughter LAN card or create an ATM LEC. When a new switch port that is not part of a default VLAN appears in the system at initialization, the system software adds that switch port to the ﬁrst default VLAN deﬁned in the system.

LANplex VLANs also allow you to modify the initial default VLAN to form two or more subsets of switch ports. If you remove the default VLAN and no other VLANs are deﬁned for the system, no ﬂooding of trafﬁc can occur.

How the LANplex® Protocol-sensitive VLANs directly affect how the LANplex system performs System Makes ﬂooding. Without protocol-sensitive VLANs, the ﬂooding process is to

Flooding Decisions forward data to all switch ports in the system. With protocol-sensitive VLANs, the ﬂooding process follows this model:

■As a frame is received that needs to be ﬂooded, it is decoded to determine its protocol type.

■If a VLAN exists for that protocol in the LANplex system and the frame’s source port is a member of the VLAN, the frame is ﬂooded according to the group of ports assigned to that VLAN.

■If a VLAN exists for that protocol in the LANplex system but the frame’s source port is not a member of the VLAN deﬁnition, then the frame is ﬂooded according to the default VLAN assigned to that port.

■If the protocol type of the received frame has no VLAN deﬁned for it in the system, the frame is ﬂooded to the Default VLAN for the receive port.

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3Com 2500 manual About VLANs

Contents

Lanplex 2500 Extended Switching User Guide 3Com Corporation 5400 Bayfront Plaza Santa Clara, California Contents Example What Is Routing?Default Route Address Resolution Protocol ARP Overlapped IP VLANs Elements IPX Routing Mbone Multicast Routing Algorithms FloodingPruning Dvmrp Metric Value Displaying Interfaces Administering interfaces LIS InterfacesAdministering Routes About Aarp 10-3 Deﬁning a Static RouteDisplaying the ATM ARP Cache 10-2 11-3 Modifying an Interface Displaying Routes Displaying the Multicast Cache11-2 11-3 12-12 What Is RMON?MIB Objects 13-4 Alarms 12-11 Support from 3Com A-4 Returning Products for Repair A-4 Monitoring Rmon When you conﬁgure your LANplex 2500 systemAbout this Guide Introduction Instructions ConventionsList conventions that are used throughout this guide Icon Type Description Information Note LANplex 2500 Documentation 801-00322-000 LANplex 2500 Software Release Notes 2-5 , Module Installation Guides About this Guide Extended FeaturesSwitching About LANplex Switching software Using Menus Bridge Menu Hierarchy IP Menu Hierarchy IPX Menu Hierarchy Appletalk Menu Hierarchy Vlan concept in LAN technology helps minimize broadcast For the network administratorVlans on About VLANs Vlans on the Lanplex System DECnet SNA Services over Ethernet EthertypeVlan Conﬁguration Protocol Suite Ethertype, Snap PID Layer 3 Addressing Information Switch Ports About VLANs Source port VLAN, so the Default Vlan is usedIndex 1 2 Data received on IP port System So the Default Vlan is usedDefault None Data received on Is flooded on Because XNS port 158.103.123.2 Data received on Is flooded on Because IP subnet158.103.122.2 On port IP subnet About VLANs Example of a Protocol-Sensitive Vlan Conﬁguration Vlan Examples Example A Vlan Conﬁguration with Servers on Separate 100BASE-T ports Example Vlans on the Lanplex System Lanplex System Bridging and Routing Subnetted Architecture with LANplex Switching Hubs Multiple Ports per Subnets with the LANplex 2500 System Routing Models Bridging Bridging in the Traditional Bridging and Routing Model Bridging in the LANplex Bridging and Routing Model Routing in the LANplex Bridging and Routing Model Bridging and Routing in the Lanplex System Routing with IP Technology IP RoutingOSI Model Hardware-conﬁgured 48-bit addresses Elements of IPRouting Section Address Classes How a Subnet Mask Is Applied to the IP Address Shows the routing table of the router in Figure Static Routes Dynamic Routes Using RIP Example of an ARP Cache Example of ARP Cache Updated with ARP Reply Transmission Errors Classical IP over Routing with Forwarding to Nodes within an LIS References Routing with IP Technology Routing with IP Multicast About IPMulticast Routing Multicast tunnel only if the Time-To-Live TTL value present To a multicast routerProvider Tunnels on page 6 for more information about tunnels Flooding Spanning Trees Reverse Path Forwarding Algorithms routing Shows a simple network with ﬁve links Simple Network Implemented Without Using Spanning Tree Multicast InterfacesWhich are described in this section Routing with IP Multicast IPX Routing NetWareEnvironment NetWare Protocols and the OSI Reference Model Be provided by protocols above IPX Protocol RIP Shows the IPX packet format How IPX Routing Works IPX Packet Routing How IPX Routing Works Service Advertising Protocol SAP ElementsIntranetwork Shows an example of a typical routing information table Aging Timer The time since the network’s last update Internetwork Service Information IPX Packet Format Routing with IPX Server Information Table Server Information Maintenance Elements of IPX Routing Routing with IPX Network Routing in AN Appletalk EnvironmentAbout AppleTalk AppleTalk Named Entities AppleTalk Networks and AppleTalk Zones Protocols AppleTalk Protocols and the OSI Reference Model Routing in AN Appletalk Environment AppleTalk Protocols Network Router Interface AppleTalk Protocols Another probe packet About AarpDescription language used by many printers Mapping for both extended and nonextended networks About Aarp Routing in AN Appletalk Environment Administering Vlans From the top level of the Administration Console, enterDisplaying Vlan Information Layer Example of a detailed display for the VLANsDescribes these statistics Fields for Vlan Information Description Index Deﬁning Vlan Information Vlan Modifying Vlan Information Information Removing Vlan Follow these steps to remove a Vlan deﬁnitionEnter the indexes for the VLANs you want to remove Example Administering Vlans Administering Administering IP Routing Administering IP Routing Ip interface summary Ip interface detail Example summary display Example detail displayDeﬁning an IP LIS Interface LIS interface example with both PVCs and SVCs Atm Route Arp Detail Accept the default yes if you want to delete the interface Modifying an InterfaceRemoving an Removing an Advertisement Address Automatically RoutesAdding a Permanent Virtual Circuit PVC Removing a Permanent Virtual Circuit PVC Timed out Static Route was statically configured LearnedInterface Status Information Description Direct Timing out Displaying Routing Table Flushing a Route Removing a Route Default route is immediately removed from the routing table ARP CacheCorresponding MAC addresses Cache String from the top level of the Administration ConsoleExample display of the contents of the ARP cache Displaying the ARP ARP cache entries are immediately removed from the table Administer the ATM ARP cacheATM ARP Servers Flushing the ARP Cache Removing an ATM ARP Server ATM switch, such as 3Com’s CELLplex 7000 system Ip atmArpServer arp Display Removing an ATM ARP Cache Entry Are modiﬁed and then forwarded through the router Bootp including Dhcp = Time = DNS =UDP Helper Flushing the ATM Displaying UDP Helper Information Enabling Disabling IP Routing Operate in any of three modes Setting the RIPEnabling Disabling Icmp Router Discovery Mode Pinging an IP Station Enter the IP address of the station you want to pingYou may receive one of the following responses Describes the IP statistics Displaying IP Statistics Administering IP Routing IP Multicast Routing Administering Methods to make this determination Enabling and Disabling DvmrpEnabling Disabling Igmp Administering IP From the top level of the Administration Console, enter Rate LimitExample multicast interface conﬁguration Enabling Multicast Interfaces Disabling Multicast Interfaces Displaying Multicast Tunnels Administration Console, enterMulticast Tunnels IP address of the remote multicast router Deﬁning a To deﬁne an IP multicast tunnel Multicast Tunnel Removing a Multicast TunnelTunnel is removed Describes the ﬁelds in the route display Displaying Routes You are prompted for the multicast source address Displaying the Multicast Cache Following display shows the multicast cache conﬁguration Describes the ﬁelds in the cache display Administering IP Multicast Routing Administering IPX Routing Is available for communications Up or unavailable Down Deﬁne an associated interfaceAddress. Each address within the network should be unique Formats and two Fddi encapsulation formats. The Ethernet Deﬁning an IPX From the Administration Console top-level menu, enter Ipx interface modify Segment. a tic is approximately 55 milliseconds Administration ConsoleKnown to the router Routers As well as the routing table Deﬁning a Static RouteConsole top-level menu, enter Ipx route remove Servers Server table using the Administration Console Deﬁning a Static Server Console top-level menu, enter Flushing Servers From the Administration Console top-level menu, enterEnter the number of hops to the server. Example Removing a Server To remove a server Forwarding Setting IPX Brackets, press Return at the prompt SettingEnhanced RIP Follow the IPX router implementation guidelines Enter the SAP mode off, passive, or active. To use the value Setting the SAP Statistics Displaying Describers the IPX RIP statistics Example below Been received Describes the IPX SAP statisticsSAP Requests SAP Entries Number of servers in the server table Ipx statistics forwarding Describes the IPX forwarding statistics No Routes Hdr ErrorsLayer header errors Errors in network layer header Administering Appletalk Routing Associated AppleTalk interface Deﬁning an Interface Displaying AppleTalk Interfaces Removing an Interface Enter the zone name Appletalk route display Following example shows a routing table display 12-7 Following example shows an Aarp cache display Removing an Entry To remove an Aarp cache entry Cache Displaying the Zone Table Enter enable or disable at the prompt Conﬁguring ForwardingZone Table by Zones Pinging an AppleTalk Node Enter enable or disable at the checksum generation promptEnter enable or disable at the checksum veriﬁcation prompt Conﬁguring Checksum Describes the AppleTalk DDP statistics you can view Following is an example of DDP summary statistics Displaying Rtmp Information An example of summary statistics is shown belowDescribes the Rtmp statistics you can view Displaying ZIP Information Describes the ZIP statistics you can view Displaying NBP Information Describes the NBP statistics you can view Remote Monitoring Rmon Technology Remote Monitoring Rmon and the Lanplex System Remote Monitoring Rmon Technology Remote Monitoring Rmon Technology History AlarmVariable and trigger an alarm Segment being monitored Information Base Management Example of an Rmon MIB Counter Object You misleading results AlarmsInstances of when counters exceed their set threshold Application for details on setting up alarms Manually Set Thresholds Generates an alarm only under the following conditions Appendix a Technical Support Appendix On-line Technical ServicesVariety of services. This appendix describes these services Technical Support Press Return to see the 3ComForum Main menu Access by Digital Modem Supplier Maintenance, application training, and support servicesSupport from Your Network U.S. and Canada, call 800 876-3266 for customer service 3ComSupport contracts are available from 3Com Numerics Index See also RIP See also SAP Mbone MIB See also Fddi station statistics Tunnels IP multicast 5-6