Internetwork Operating System Release 10.2 cisc EM Bridging Software Release O2 September 1994 Corporate Headquarters 170 West Tasman Drive San Jose CA 95134-1706 USA Phone 408 526-4000 Fax 408 526-4100 Customer Order Number TRN-IRSC-1O.2 Text Part Number 2O91O1 The and and other technical information the products specifications configurations regarding products contained in this manual are subject to change without notice Alt statements technical information and recommendations contained in this manual are believed to be accurate and reliable but are without of and must take full for their presented warranty any kind express or implied users responsibility application of any products specified in this manual This radiate radio if not installed and used in equipment generates uses and can frequency energy and accordance with the instruction manual for this device may cause interference to radio communications This equipment has been tested and found to comply with the limits for Class computing device which reasonable pursuant to Subpart of Part 15 of FCC Rules are designed to provide protection against such interference when operated in commercial environment of this in residential is in which their Operation equipment area likely to cause interference case users at own expense will be required to take whatever measures may be required to correct the interference will The following third-party software may be included with your product and be subject to the software license agreement The Cisco implementation of TCP header compression is an adaptation of program developed by the University of California Berkeley UCB as part of UCBs public domain version of the UNIX operating system All rights reserved Copyright 1981 Regents of the University of Califomia Network Time Protocol NTP Copyright 1992 David Mills The University of Delaware makes no representations about the suitability of this software for any purpose Point-to-Point Protocol Copyright 1989 Carnegie-Mellon University All rights reserved The name of the University may not be used to endorse or promote products derived from this software without specific prior written permission The Cisco implementation of TN3270 is an adaptation of the to3270 curses and termcap programs developed by the University of California Berkeley UCB as part of UCBs public domain version of the UNTX operating system All rights reserved Copyright 1981-1988 Regents of the University of California Cisco incorporates Fastmac software in some Token Ring products Fastmac software is licensed to Cisco by Madge Networks Limited XRemote is trademark of Network Computing Devices Inc Copyright 1989 Network Computing Devices Inc Mountain View California NCD makes no representations about the suitability of this software for any purpose The Window System is trademark of the Massachusetts Institute of Technology Copyright 1987 Digital Equipment Corporation Maynard Massachusetts and the Massachusetts Institute of Technology Cambridge Massachusetts All rights reserved THIS MANUAL AND THE SOFFWARE OF THE ABOVE-LISTED SUPPLIERS ARE PROVIDED AS IS WITH ALL FAULTS CISCO AND THE ABOVE-NAMED SUPPLIERS DISCLAIM ALL WARRANTIES EXPRESSED OR IMPLIED INCLUDING THOSE OF MERCHANTABILITY AND FITNESS FOR PARTICULAR PURPOSE OR ARISING FROM COURSE OF DEALING USAGE OR TRADE PRACTICE IN NO EVENT SHALL CISCO OR ITS SUPPLIERS BE LIABLE FOR ANY INDIRECT SPECIAL CONSEQUENTIAL OR INCIDENTAL DAMAGES INCLUDING WITHOUT LIMITATION LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THIS MANUAL EVEN IF CISCO HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES Notice of Restricted Rights disclosure Use duplication or by the Government is subject to restrictions as set forth in subparagraph of the Commercial Computer Software Restricted Rights clause at FAR 52.227-19 and subparagraph c1ii of the Rights in Technical Data and Compuler Software clause at DFARS 252.227- 13 The information in this 70 manual is subject to change without notice Without Access Compromise Catalyst CiscoFusion CiscoWorks Internelwork Operating System 105 Netscape The Packet SMARTnet UniverCD and Workgroup Director Workgroup Stack are trademarks and Cisco Systems and the Cisco logo are registered trademarks of Cisco Systems Inc Alt other services products or mentioned in this document are the trademarks service marks registered trademarks or registered service marks of their respective owners Bridging Copyright 1994 Cisco Systems Inc All rights reserved Printed in USA TABLE OF CONTENTS Chapter Bridging Overview 1-1 Chapter Transparent Bridging 2-1 Chapter Source Route Bridging 3-1 Chapter Mixed-Media Bridging 4-1 Chapter Remote Source-Route Bridging 5-1 Cisco Systems Inc 1994 Table of Contents iii iv Bridging ver 10.2 CHAPTER Brdgng Overview Cisco Systems Inc 1994 Bridging Overview 1-1 Objecflves Upon compeflon of this modue you wUH be abHe to perform the foUowng tasks Describe the basic functions of bridge Identify the various bridge types supported by Cisco Describe when to implement each of the bridge types 1994 12 Bridging Cisco Systems Inc Routing and Bridging RoutabHe Protocos NonroutabHe ProtocoHs FRAME Routing is based on the logical addresses contained in the network layer of the OSI reference model routable protocol may be routed or in some cases it may be bridged such Some protocols as LAT Local Area Transport and MOP Maintenance Operation Protocol and NetBIOS have no logical addressing and therefore cannot be routed The nonroutable protocols must be bridged Cisco Systems Inc 1994 Bridging Overview 1-3 NonRoutabe Protocos ji Routed Routed Bridged Bridged Nonroutabe protocos must be brdged station using routable protocol station using bridgable-only protocol Cisco Inc 1994 1-4 Bridging Systems SourceRoute Brdgng Uses RFs to define path to desfinaflon Hosts must support SRB Source-Route Bridging SRB Specifies communication between two token rings Path information is carried in RIF Path information is gathered by an explorer packet Cisco Systems Inc 1994 Bridging Overview 15 Transparent Bridging Brdge transparent to hosts defines the connection of two Ethernet domains Transparent Bridging Cisco Systems Inc 1994 16 Bridging EncapsuNated Brdgng Brdge frames are passed over Sera or FDD Encapsulated Bridging provides for the encapsulation of transparently bridged frames over wide-area network WAN and local-area network LAN links such as FDDI Encapsulated bridging sometimes referred to as remote transparent bridging Cisco Systems Inc 1994 Bridging Overview 1-7 SRT and SRITLB SRT Source Route Transparent Simultaneous Source Route and Transparent Bridging SRITLB Source Route Translational Bridging Translates between Source Route and Transparent Bridging Source-Route Transparent Bridging SRT Defines source-route bridging as an option on top of transparent bridging transfer Handles both source-route and transparent bridging at the same time one packet per Keeps the Token Ring and Ethernet domains separate Source-Route Translational Bridging SRITLB Brings the Token Ring and Ethernet domains together Enables device on Token Ring to communicate seamlessly with device on Ethernet Routing is more common solution Cisco 1994 1-8 Bridging Systems Inc Remote Source Route Bridging Token cAll Token\ rj Arbätrary mecila between SRBs Remote Source Route Bridging RSRB Provides serial tunneling of Token Ring frames Enables Token Ring SRB frames to be encapsulated over an arbitrary media Cisco Systems Inc 1994 Bridging Overview 1-9 Summary TB Transparent Bridging No RIFS SRB SourceRoute Bridging RIFs Token Ring Token Ring SRT Source-Route Transparent Bridging Ethernet Ethernet and Token Ring Token Ring SR/TLB Source-Route Translational Bridging Ethernet Token Ring RSRB Token Ring Arbitrary Media Token Ring Cisco Systems Inc 1994 1-10 Bridging CHAPTER Transparent Bridging Cisco Systems Inc 1994 Transparent Bridging 2-1 Objectives Upon compleflon of thHs moduHe you wUh be abbe to perform the foflowing tasks Describe the basic functions of transparent bridging Enable and configure transparent bridging on the Cisco router Monitor transparent bridging operation in the router 2-2 Bridging Cisco Systems lnc 1994 Transparent Brdgng EOE1 Three major funcflons Learning Forwarding/filtering frames Loop avoidance Cisco Systems Inc 1994 Transparent Bridging 2-3 Learning E0 0260.8c01.llll E0 0260.8c01.2222 El 0260 8c01 3333 _______ El 0260.8c01 .4444 0260.8c01 .1111 0260.8c01 .4444 0260.8c01 .3333 0260.8c01 .2222 Source MAC addresses are assocated wth ports 2-4 Bridging Cisco Systems Inc 1994 Forwarding EO 0260.8c01.llll EG 0260.8c01 .2222 O26O.8cO1.3333 El 0260.8c01 .4444 0260.8c01 .1111 0260.8c01 .4444 El 0260.8c01 .2222 0260.8c01 .3333 Traffic propagated to specffic destnaflons Cisco Systems Inc 1994 Transparent Bridging 2-5 FUterng EO O26O8cOl.llll EO 0260.8c01 .2222 El 0260.8c01 .3333 El 0260.8c01 .4444 0260.8cOl .1111 0260.8c01 .4444 El 0260.8c01 .2222 0260.8c01 .3333 Congeston contro through network knowHedge This does not refer to filtering as it is used in the sense of an access list Here filtering describes the normal of which operation transparent bridge does not forward packets unnecessarily 2-6 Bridging Cisco Systems inc 1994 Topoogcal Loops 11t if ii Brdged network can have mutipHe paths Topological loops can result in broadcast storms Cisco Systems Inc 1994 Transparent Bridging 2-7 Loop Avoidance Spannng tree aDgorthms düsabe nterfaces Transparent spanning tree protocols DEC IEEE 802.1D The protocol elects root bridge Each bridge selects the lowest