3Com 3800 Spanning Tree Domains

7-4 CHAPTER 7: SPANNING TREE PROTOCOL (STP)

The Root Bridge generates BPDUs on all ports at a regular interval

known as the Hello Time. All other bridges in the network have a Root

Port. This is the port that costs the least in getting to the Root Bridge,

and it is used for receiving the BPDUs initiated by the Root Bridge.

Stabilization

After all bridges on the network have determined the conﬁguration of

their ports, each bridge only forwards trafﬁc between the Root Port

and the ports that are the Designated Bridge Ports for each network

segment to which they are attached. All other ports are blocked, which

means that they are prevented from forwarding trafﬁc.

Reconﬁguration

In the event of a network failure (such as a segment going down) the

STP system reconﬁgures the network to adjust for the changes. If the

topology of the network changes, the Root Bridge sends out an SNMP

trap.

Spanning Tree

Domains The Switch 3800 can be partitioned into multiple virtual bridges. Each

virtual bridge can run an independent spanning tree instance. Each

spanning tree instance is called a Spanning Tree Domain (STPD). Each

STPD has its own Root Bridge and active path. Once the STPD is

created, one or more VLANs can be assigned to it.

A port can belong to only one STPD. If a port is a member of multiple

VLANs, then all those VLANs must belong to the same STPD.

The key points to remember when conﬁguring VLANs and STP are the

following:

■Each VLAN forms an independent broadcast domain.

■STP blocks paths to create a loop-free environment.

■When STP blocks a path, no data can be transmitted or received on

the blocked port.

SW3800.BK Page 4 Tuesday, May 5, 1998 5:20 PM

Contents

Main 3Com Corporation 5400 Bayfront Plaza Santa Clara, California 95052-8145 CSA Statement FCC Statement Electromagnetic Compatibility VCCI Statement Information To The User Page C ONTENTS VERVIEW 3800 O WITCH NSTALLATION WITCH S HE I ETUP AND OMMANDS C Page PANNING OUTING R NICAST ROTOCOL REE 9 A B UPPORT ECHNICAL D Page A BOUT T HIS G Finding Information in This Guide This table shows where to nd specic information in this guide. Conventions guide. Table 1 Notice Icons Table 2 Text Conventions Command Syntax Symbols Table 3 Command Syntax Symbols Line-Editing Commands Related Publications Page 1 About the Switch 3800 Summary of Features Page Dual-homed Page Network Conguration Example Page Switch 3800 Front View Table 1-1 Media Types and Distances Table 1-2 Switch 3800 LEDs Switch 3800 Rear View Factory Defaults Table 1-3 Switch 3800 Factory Defaults 2 Following Safety Information Determining the Switch 3800 Location Installing the Switch 3800 Page Connecting Equipment to the Console Port Figure 2-2 shows the pin-outs for a 9-pin to RS-232 25-pin null modem cable. Figure 2-3 shows the pin-outs for a 9-pin to 9-pin PC-AT serial null modem cable. Powering-up the Switch Checking the Installation Logging on for the First Time Page Page 3 Security Access Levels Page Page Methods of Managing the Using Telnet Page Page Using SNMP Page Page Table 3-4 describes SNMP conguration commands. Table 3-4 SNMP Conguration Commands Checking Basic Connectivity Conguring Ports Page Load Sharing Page SmartRedundancy Port Commands Table 3-8 Port Commands (continued) 4 Understanding the Command Syntax Page Page Line-Editing Commands command-line interface. Table 4-1 Command Syntax Symbols (continued) Table 4-2 Line-Editing Commands Command History Substitution can display a list of these commands by typing Common Commands Commands specic to a particular feature are described in the other chapters of this guide. Table 4-3 Common Commands Switch 3800 Commands General Switch Commands Table 4-4 describes general Switch commands. Table 4-4 General Switch Commands User Account Commands Table 4-5 describes user account commands. Table 4-4 General Switch Commands (continued) Table 4-5 User Account Commands Switch Management Commands Table 4-6 describes Switch management commands Table 4-6 Switch Management Commands VLAN Commands Table 4-7 describes VLAN commands. Table 4-6 Switch Management Commands (continued) Table 4-7 VLAN Commands Protocol Commands Table 4-8 describes protocol commands. FDB Commands Table 4-9 describes FDB commands. Table 4-8 Protocol Commands Table 4-9 FDB Commands Port Commands Table 4-10 describes port commands. Table 4-9 FDB Commands (continued) Table 4-10 Port Commands PACE Commands Table 4-11 describes PACE commands. Table 4-10 Port Commands Table 4-11 PACE Commands STP Commands Table 4-12 describes STP commands. Table 4-12 STP Commands Table 4-12 STP Commands (continued) Basic IP Commands Table 4-13 describes basic IP commands. Table 4-13 Basic IP Commands IP ARP Commands Table 4-14 describes IP ARP commands. Table 4-13 Basic IP Commands (continued) Table 4-14 IP ARP Commands IP Route Table Commands Table 4-15 describes IP route table commands. ICMP Commands Table 4-16 describes the commands used to congure the ICMP protocol. Table 4-15 IP Route Table Commands Table 4-16 ICMP Commands Table 4-16 ICMP Commands (continued) RIP Commands Table 4-17 describes the commands used to congure the RIP protocol. Table 4-17 RIP Commands Table 4-17 RIP Commands (continued) Logging Commands Table 4-18 describes Switch logging commands. Table 4-18 Logging Commands Conguration and Image Commands Table 4-19 describes conguration and image commands. Table 4-18 Logging Commands (continued) Table 4-19 Conguration and Image Commands Table 4-19 Conguration and Image Commands (continued) 5 Overview of Virtual LANs Page Marketing Finance Page Accounting Engineering Page Figure 5-4 illustrates the physical view of a network that uses tagged and untagged trafc. Figure 5-4 Physical diagram of tagged and untagged trafc Figure 5-5 shows a logical diagram of the same network. Figure 5-5 Logical view of tagged and untagged trafc Marketing Page Page Page Conguring VLANs on the Switch 3800 Table 5-1 describes the commands used to congure a VLAN. VLAN Conguration Examples The following example creates a port-based VLAN named accounting, assigns the IP address 132.15.121.1, and assigns ports 1, 2, 3, and 6 to it: Table 5-1 VLAN Conguration Commands Displaying VLAN Settings Page Deleting and Resetting VLANs Page 6 D FDB Overview of the Page Conguring FDB Entries Displaying FDB Entries Removing FDB Entries 7 Overview of the Spanning Tree Protocol Page Page Spanning Tree Domains Page STP Congurations STPD 1 STPD 2 Sales, Personnel, Marketing Manufacturing, Engineering, Marketing Sales, Personnel, Manufacturing, Engineering, Marketing Page STP Congurations to Avoid Marketing & Sales Marketing, Sales & Engineering Sales & Engineering Creating STP Domains Marketing & Sales Marketing, Sales & Engineering Sales & Engineering Enabling STP on the Switch Conguring STP Table 7-1 STP Conguration Commands (continued) Displaying STP Settings Sample output from the command is as follows: Disabling and Resetting STP 8 Overview of IP Unicast Routing Page Page Conguring IP Unicast Routing Verifying the IP Unicast Routing Conguring DHCP/BOOTP Relay Table 8-1 describes the commands used to congure basic IP settings on the Switch. Table 8-1 Basic IP Commands Table 8-2 describes the commands used to congure the IP route table. Table 8-3 describes the commands used to congure RIP. Table 8-1 Basic IP Commands (continued) Table 8-2 Route Table Conguration Commands Table 8-3 RIP Conguration Commands Table 8-3 RIP Conguration Commands (continued) Table 8-4 describes the commands used to congure the ICMP protocol. Table 8-3 RIP Conguration Commands (continued) Table 8-4 ICMP Conguration Commands Routing Conguration Example Figure 8-2 Unicast Routing Conguration Example = IP traffic = NetBIOS traffic Displaying Router Settings commands listed in Table 8-5. Table 8-5 Router Show Commands Resetting and Disabling Router Settings Table 8-5 Router Show Commands (continued) Table 8-6 Router Reset and Disable Commands Table 8-6 Router Reset and Disable Commands (continued) 9 S Status Monitoring Page Page Port Statistics Page Port Errors Switch Logging Page Page Logging Commands The commands described in Table 9-4 allow you to do the following: Table 9-4 Logging Commands RMON Page Page Page Page Page 10 O Upgrading the Software Saving Conguration Changes Boot Option Commands Page A Important Safety Information Page Page Linformation de Scurit Importante Page Page Page Wichtige Sicherheitsinformat ionen Page Page Page Page B Physical Dimensions Page C LEDs Using the Command-Line Interface Page Page Page Page D Online Technical Services Page Support from Your Network Supplier D-4 APPENDIX D: TECHNICAL SUPPORT Support from 3Com Regional Sales Office Telephone Number Regional Sales Office Telephone Number Returning Products for Repair Page G Page Page Page I Numerics A B C L M N O P T U V W Page 3Com Corporation LIMITED W H S STANDARD WARRANTY S W ARRANTIES E L IMITATION OF L IABILITY G OVERNING L AW